A protocol to improve analgesia use in the accident and emergency department

In this experiment, intracellular K+ concentration ([K+]i) and ATPase activity of myocardiocytes were measured in early stage of burn injury. Comparing with control group, it was found that, 1. [K+]i were decreased after burn injury, [K+]i of 1st, 3rd, 8th and 24th hours were decreased to 96.2 +/- 1.3%, 85.8 +/- 1.3%, 65.9 +/- 1.0% and 73.7 +/- 1.1% of normal, respectively. 2. Cardiac sarcolemma total ATPase, Mg(2+)-ATPase and Na(+)-K(+)-ATPase activities were all reduced significantly at 8th hour after injury. These results suggest that, burn injury accelerates K+ efflux current, but inhibits K+ influx current, and the reduction of Na(+)-K(+)-ATPase activity is one reason of decrease of [K+]i after injury.     

Relationship between fluid transport and in situ inhibition of Na(+)-K+ adenosine triphosphatase in corneal endothelium

PURPOSE: To examine the relationship between the activity of the sodium pump of the corneal endothelium and corneal thickness. It was postulated that because inhibition pressure of the stroma decreases as thickness increases, a partially inhibited sodium pump would result in a new steady-state thickness of the cornea when reduced rates of fluid influx and efflux were equal. Measurements of physiologic behavior and biochemical activity were to be made in the same tissue and thus establish the relationship directly. METHODS: Rabbit corneas were superfused with a bicarbonate Ringer solution containing different concentrations of ouabain. Exposure to ouabain was either continuous for 4 hours or for an initial 10 minutes followed by ouabain-free superfusion. Thickness was measured, and, after superfusion, endothelium was removed from the corneas, sonicated, and assayed for Na(+)-K+ adenosine triphosphatase (ATPase) activity without further addition of ouabain to the assay medium. Thickness was also measured during superfusion with suboptimal concentrations of Na+ or HCO3- and with brefeldin A, an inhibitor of protein trafficking. RESULTS: Continuous exposure to ouabain caused corneas to swell, but no new steady-state thickness was reached. At low concentrations, swelling rates increased with time, as did the extent of inhibition of the Na(+)-K+ ATPase. With only a 10-minute exposure to ouabain, swelling rates with 10(-4) M to 10(-5) M decreased with the duration of ouabain-free superfusion. Similar swelling curves were obtained by reductions in Na+ or HCO3- concentrations in the superfusion medium, indicating that partial inhibition of the endothelial fluid transport processes, whether via the Na(+)-K+ ATPase or by suboptimal ionic conditions, led toward a new equilibrium thickness of the cornea. However, when superfusion was continued for more than 4 hours, the corneas exposed for 10 minutes to 3 x 10(-5) M or lower-concentration ouabain showed increasing Na(+)-K+ ATPase activity and began to thin, indicating a recovery of fluid transport capability. This recovery was blocked by addition of brefeldin A during the ouabain-free superfusion. CONCLUSIONS: Inhibition of Na(+)-K+ ATPase by low concentrations of ouabain increases with time. Temporary exposure to ouabain causes swelling at rates that decline with time as ouabain dissociates from enzyme sites. This dissociation, together with the turnover of Na(+)-K+ ATPase in the plasma membrane, can lead to recovery of normal thickness in ouabain-exposed corneas. Twenty percent of Na(+)-K+ ATPase in the endothelium is estimated to be intracellular, and about 20% of the activity can be inhibited without inducing swelling.     

An empirical study of object relations in adult children of depressed elderly mothers

The present report confirms the presence of Na(+)-K(+)-Mg2+ ATPase in the erythrocyte membranes of the frog Rana balcanica (previously Rana ridibunda) (Schneider et al. 1993; Sofianidou et al. 1994). The Na(+)-K(+)-Mg2+ ATPase activity was 60% reduced by the presence of ouabain. The pH optimum was 8.0, the optimum Mg2+:ATP concentration ratio was 2.2:1. The existence of an ATPase with a high K(m) for ATP (1.48 mmol/l) was postulated. At pH 7.4 and 8.0, the adenine nucleotide pattern of glucose-depleted erythrocytes showed a characteristic reduction in ATP contents. Adenine nucleotide concentrations were higher at pH 7.4 than at pH 8.0. Ouabain inhibited ATP breakdown at both pH values studied. The strongest inhibition was observed at pH 7.4. The decline of the total contents of adenine nucleotides appears to be determined by the rate of AMP breakdown.     

Na(+)-K+ ATPase concentration in different adult rat skeletal muscles is related to oxidative potential

To investigate the relationship among fibre type, oxidative potential, and Na(+)-K+ ATPase concentration in skeletal muscle, adult male Wistar rats weighing 259 +/- 8 g (mean +/- SE) were sacrificed and the soleus (SOL), extensor digitorum longus (EDL), red vastus lateralis (RV), and white vastus lateralis (WV) removed. These muscles were chosen as being representative of the two major fibre type populations: slow twitch (SOL) and fast twitch (EDL, RV, WV) and exhibiting either a high (SOL, EDL, RV) or low (WV) oxidative potential. Na(+)-K+ ATPase concentration (pmol.g-1 wet weight), measured by the [3H]ouabain binding technique, differed (p < 0.01) only between the WV (238 +/- 7.9) and the SOL (359 +/- 9.6), EDL (365 +/- 10), and RV (403 +/- 12). Similarly, muscle oxidative potential as measured by the maximal activity of citrate synthase was different (p < 0.01) only between the WV and the other three muscles. Citrate synthase activity (mumol.min-1.g-1 wet weight) was 4.0 +/- 0.7, 12.3 +/- 0.9, 9.1 +/- 0.7, and 11.3 +/- 1.0 in the WV, SOL, EDL, and RV, respectively. These results indicate that Na(+)-K+ ATPase concentration is not related to the speed of contraction but to the oxidative potential of the muscle. Since chronic activity is a primary determinant of oxidative potential, it would be expected that increases in Na(+)-K+ ATPase would accompany increases in muscle utilization.     

Effect of time in culture on modulation of Na(+)-K(+)-ATPase activity in rat alveolar type II cells

To determine the effect of time in culture on epithelial cell function, we evaluated the modulation of Na(+)-K(+)-ATPase activity in rat alveolar type II cells in culture. Ouabain sensitivity testing revealed that the alpha-1 predominance in the enzyme's isoforms was maintained over the 120 hours in culture. Basal Na(+)-K(+)-ATPase activity in the whole cell homogenate did not differ significantly between cells cultured for 48 hours and those cultured for 120 hours. Terbutaline (10 mM) did not activate Na(+)-K(+)-ATPase in the cells cultured for 48 hours, but, it significantly increased the activity of this enzyme in the cells cultured for 120 hours cells cultured for 48 hours, produced intracellular cyclic AMP after exposure to 10 mM of terbutaline. These results indicate that the coupling between Na(+)-K(+)-ATPase and the beta-adrenergic pathway in alveolar type II cells can be influenced by the time in cell culture.     

Influence of ethanol on cadmium accumulation and its impact on lipid peroxidation and membrane bound functional enzymes (Na+, K(+)-ATPase and acetylcholinesterase) in various regions of adult rat brain

Influence of ethanol on cadmium accumulation and its effect on metallothionein induction, binding of cadmium to metallothionein, lipid peroxidation and membrane bound functional enzymes such as (Na(+)-K+)-ATPase and acetylcholinesterase in various regions of adult rat brain was investigated. Ethanol (2 g/kg body wt) and cadmium (1 mg/kg body wt) were administered alone as well as in combination to different groups of rats, i.p., for a period of 1 week. It was observed that cadmium when co-administered with ethanol led to pronounced increase in cadmium accumulation in various regions of the brain. This ethanol induced accumulation of cadmium did not induce the synthesis of metallothionein and also did not bind to this protein in brain and mainly was present as non-metallothionein bound cadmium. It lead to a significant increase in lipid peroxidation and inhibition of membrane bound functional enzymes; (Na(+)-K+)-ATPase and acetylcholinesterase in various regions of the brain indicating functional impairment. The results of the present study imply that ethanol renders the adult brain more susceptible to cadmium neurotoxicity. Corpus striatum and cerebral cortex are more vulnerable regions than other areas of the brain.     

Myocardial digoxin uptake: dissociation between digitalis-induced inotropism and myocardial loss of potassium

The time course of myocardial uptake of digoxin, of increase in inotropic effect and of changes in myocardial potassium content were studied following a single intravenous dose of digoxin. Nineteen dogs with intact circulation were investigated by the use of a biopsy technique which allowed samplings before and 10, 30, 60, and 90 min after administration of digoxin. The myocardial concentration of digoxin was 196 X 10(-9) mol/kg 10 min after administration of digoxin. Uptake continued at a slower rate, maximum concentration being 293 X 10(-9) mol/kg at 60 minutes. The inotropic effect increased parallel with the uptake of digoxin; 10 min after digoxin, contractility was 127% of the control value and this increased to 139% at 90 minutes. Myocardial potassium content was slightly increased 10 min after digoxin, suggesting an initial stimulation of membrane Na+-K+ ATPase. A subsequent significant fall in the myocardial potassium content probably reflects ATPase inhibition. The temporal dissociation between the early onset of the positive inotropic effect and the delayed inhibition of membrane Na+-K+ ATPase indicates that inotropism of digitalis glycosides is not mediated by the same binding site as that responsible for inhibition of Na+-K+ ATPase.     

Peripheral nerve blocks improve analgesia after total knee replacement surgery

Using an in vitro cell system and Cs+ NMR techniques we were able to show that porcine aortic endothelial cells (PAEC) reduce their Na(+)-K(+)-ATPase activity upon an increase in intracellular cAMP. Reduction in the pump rate was due to phosphorylation of the alpha-subunit of the ATPase as shown by immunoprecipitation. Apart from a pump inhibiton using 8-Br-cAMP and IBMX, we were also able to show that changes in the Na(+)-K(+)-ATPase activity could be mediated by the adenosine-A2 and prostaglandin receptor agonists 5'-N-Ethylcarboxamidoadenosine and Iloprost, respectively. Parallel to a decrease in pump activity we also observed a decrease in intracellular Cs+, indicating opening of K+ channels.     

Relationship of red blood cell ion transport alterations and serum lipid abnormalities in Lyon genetically hypertensive rats

Alterations of Na+ and K+ transport in erythrocytes of hypertensive humans or animals are often associated with abnormal lipid metabolism. The aim of the present study was to investigate red blood cell ion transport in Lyon inbred strains selected from Sprague-Dawley rats for different blood pressure levels. Lyon strains are characterized by important metabolic changes, including plasma lipid abnormalities. Serum triglycerides, cholesterol, and uric acid as well as red blood cell Na+ and K+ (Rb+) transport mediated by Na(+)-K+ pump or Na(+)-K+ cotransport and cation leaks were studied in hypertensive (LH), normotensive (LN), and low blood pressure (LL) Lyon rats aged 12 weeks. Increased erythrocyte Na+ content (Nai+) and higher levels of serum triglycerides, cholesterol, and uric acid were demonstrated in LH rats compared with LN animals. Nevertheless, at this age serum triglycerides and erythrocyte Nai+ of LL rats were even higher than those of LH animals. There were no significant differences between Lyon strains in either Na(+)-K+ pump activity or bumetanide-resistant (BR) cation leaks. The activity of bumetanide-sensitive (BS) Na(+)-K+ cotransport mediating inward Na+ movement was highest in LL rats and lowest in LH animals. In Lyon rats, Nai+ was positively related to serum triglycerides, whereas blood pressure correlated positively with BR Na+ leak and negatively with BS net Na+ uptake. A similar association of erythrocyte Nai+ with serum triglycerides was also observed in Prague hereditary hypertriglyceridemic rats (HTG) that were selected from Wistar rats for high plasma triglycerides. The major difference of the two forms of genetic hypertension associated with abnormal lipid metabolism was in BS net Na+ uptake, which was enhanced in HTG but reduced in LH rats. This was probably due to differences in plasma cholesterol, which was elevated in LH but not in HTG animals. Our study in Lyon rats confirmed the positive association of blood pressure with Na+ leak as a characteristic feature of genetic hypertension.     

Transjugular intrahepatic portosystemic shunt: a medical perspective

We studied the ability of cilostazol (CL), an antithrombotic and vasodilating agent, to prevent functional, structural and biochemical abnormalities including delayed motor nerve conduction velocity (MNCV), morphological changes in myelinated fibers, and decreased Na(+)-K(+) -ATPase activity in the peripheral nerves of rats with streptozotocin (STZ)-induced diabetes. Cilostazol treatment (30 mg/kg/day p.o.) for 10 weeks significantly prevented the delay in MNCV in the tail nerve, and morphometric analysis of the sural nerves revealed that this dose of cilostazol had a significant effect on reduction of average size of myelinated fibers. In untreated diabetic rats, cyclic AMP content and Na(+)-K(+)-ATPase activity of peripheral nerve were each significantly less than in normal control rats. Cilostazol (30 mg/kg/day) prevented reduction of Na(+)-K(+)-ATPase activity. Decrease in cyclic AMP content was completely prevented with both doses of cilostazol (30 and 10 mg/kg/day). These findings suggest that cilostazol may have beneficial effects in the treatment of diabetic neuropathy, possibly via improvement of nerve Na(+)-K(+) -ATPase activity and cyclic AMP content. Cilostazol may thus be a potent drug for the clinical treatment of diabetic neuropathy.     

Expression of D1 receptor mRNA in projections from the forebrain to the ventral tegmental area

The presence of subunit proteins, 1H9 for the alpha-subunit and 2B6 for the beta-subunit, of H(+)-K+ ATPase and its activity in tubulovesicles and intracellular canaliculi of gastric parietal cells were immunocytochemically and enzyme cytochemically examined. Specimens were taken from healthy human volunteers by endoscopic biopsy in resting, tetragastrin-stimulated and omeprazole-inhibited conditions. H(+)-K+ ATPase was present in both intracellular canaliculi and tubulovesicles in these three conditions. Gold particles of the alpha-subunit decreased in number, and those showing the beta-subunit increased under both gastrin-stimulating and omeprazole-inhibiting conditions compared with parietal cells in the resting state. We suggest that the administration of tetragastrin and omeprazole alter the turnover rate of each subunit of H(+)-K+ ATPase, resulting in the difference of the proportions of alpha- and beta-subunits. Moreover, the activity of H(+)-K+ ATPase was detected strongly beneath the membrane of microvilli and weakly in that of tubulovesicles under these three conditions. After 7 days of daily oral omeprazole intake, H(+)-K+ ATPase in parietal cells were detected in intracellular canaliculi and tubulovesicles. However, the H(+)-K+ ATPase activity in tubulovesicles was diminished 1 h after omeprazole intake, and the activity in intracellular canaliculi was completely inhibited even 3 h after omeprazole administration. These results show that omeprazole inhibited the H(+)-K+ ATPase activity in both intracellular canaliculi and tubulovesicles.     

Calbindin D-28k and monoamine oxidase A immunoreactive neurons in the nucleus basalis of Meynert in senile dementia of the Alzheimer type and Parkinson''s disease

The lungs must be kept "dry" for efficient gas exchange. The mechanisms that contribute to clear alveoli from fetal lung fluid at birth are still present during adult life and allow recovery from alveolar flooding. It has recently been shown with the use of different approaches in vitro, as well as in vivo, that alveolar epithelium performs solute-coupled fluid transport. Fluid absorption from alveoli occurs chiefly as a result of active transepithelial Na+ transport. The mechanisms of Na+ transport have been partly elucidated; Na+ enters alveolar cells through apical Na+ channels and Na(+)-coupled solute transporters and is pumped out at the basolateral membrane by a Na(+)-K(+)-adenosinetriphosphatase (ATPase). Transepithelial Na+ transport and fluid absorption are stimulated by beta-adrenergic agonists, with adenosine 3',5'-cyclic monophosphate being the likely intracellular second messenger. K+ is probably secreted into alveoli because its concentration in the epithelial lining fluid is larger than expected for passive distribution. K+ channels have been described that, in conjunction with Na(+)-K(+)-ATP-ase, might provide pathways for active transport. Active proton secretion or bicarbonate absorption have been reported, which may explain the low pH of the alveolar epithelial lining fluid. It is probable that active solute transports are the main determinants of epithelial lining fluid depth and composition. A challenge for the future is to understand how this homeostasis is achieved.     

Effects of selective head cooling on brain cell membrane activity during postischemic reperfusion

OBJECTIVE: To examine the effect of selective head cooling (SHC) on brain cell membrane activity involving ATPase, phospholipase A2, content of total membrane phospholipids during postischemic reperfusion, so as to elucidate the possible underlying mechanism on resuscitating effect of SHC. MATERIALS AND METHODS: Complete cerebral ischemia (CCI) was induced by the four-vessel model. 56 New Zealand rabbits were allocated randomly into two groups, non-ischemic control group had 30, 180 and 360 minutes reperfusion after CCI (n = 8); and SHC group with the same ischemic-reperfusion insult were all treated with SHC (28 degrees C, surface cooling method). Changes of Na+, K(+)-ATPase, Ca2+, Mg(2+)-ATPase, phospholipase A2, total phospholipids of brain cell membrane were observed. Comparison of data between two groups was made by Students' t test. RESULTS: Compared with non-ischemic controls following 30 minutes CCI, activities of Na+, K(+)-ATPase stepwisely decreased at 30, 180 and 360 minutes, Ca2+, Mg(2+)-ATPase dropped at 180 and 360 minutes, phospholipidase A2 increased markedly at 30, 180, 360 minutes, and total phospholipids decreased at 180 and 360 minutes reperfusion (P < 0.01). Selective head cooling inhibited all the above changes significantly (P < 0.01). CONCLUSION: The results suggest that selective head cooling initiated soon after reperfusion is beneficial for brain cell membrane function recruitment, which provides favourable effects on the damaged but still remediable brain cells for their resuscitation.     

Arginine vasopressin release inhibitor RU51599 attenuates brain oedema following transient forebrain ischaemia in rats

RU51599 is an arginine vasopressin (AVP) release inhibitor and a selective kappa opioid agonist which has a pure water diuresis effect without associated electrolyte excretion. The effect of RU51599 on brain oedema following transient forebrain ischaemia in rats was examined. Under microscopy, the visible vertebral arteries at the second vertebra could be easily electrocauterized and completely cut by microscissors to yield complete cessation of circulation of both vertebral arteries. Transient forebrain ischaemia was induced by this improved highly reproducible technique of four-vessel occlusion model. Forty-three male Wistar rats were separated into six groups; saline-treated (1 ml/kg) normal rats (n = 10), RU51599-treated (1 mg/kg) normal rats (n = 4), saline-treated (1 ml/kg) rats with complete occlusion of both vertebral arteries (n = 5), RU51599-treated (1 mg/kg) rats with complete occlusion of both vertebral arteries (n = 5), saline-treated (1 ml/kg) rats with both complete occlusion of both vertebral arteries and carotid occlusion bilaterally during 45 minutes followed by 60 minutes of reperfusion (n = 11), RU51599-treated (1 mg/kg) rats with both complete occlusion of both vertebral arteries and carotid occlusion bilaterally during 45 minutes followed by 60 minutes of reperfusion (n = 8). The brain water content was determined by the dry-wet weight method. Cerebral blood flow was monitored during ischaemia and reperfusion was performed by laser Doppler flowmetry to make sure to obtain reversible forebrain ischaemia. Effects of RU51599 on concentration of glutamate released from the hippocampal CA1 of rats subjected to 5 minutes four-vessel occlusion and 60 minutes of reperfusion were also investigated by the microdialysis method. This modified four-vessel occlusion method produced reversible forebrain ischaemia with a high level of success. Bilateral carotid occlusion followed by 60 minutes reperfusion caused a significant increase in brain water content (P < 0.01), which was significantly attenuated by RU51599 (P < 0.01). These findings indicate that the AVP-release inhibitor RU51599 reduced brain oedema following transient forebrain ischaemia in rats.     

Kaliuretic peptide: the most potent inhibitor of Na(+)-K+ ATPase of the atrial natriuretic peptides

The present investigation was designed to determine whether atrial natriuretic peptides consisting of amino acids 1-30 (i.e. long-acting natriuretic peptide), 31-67 (vessel dilator), 79-98 (kaliuretic peptide), and 99-126 [atrial natriuretic factor (ANF)] of the 126 amino acid ANF prohormone inhibit sodium-potassium-ATPase as part of their mechanism(s) of action for producing a natriuresis and/or kaliuresis. Kaliuretic peptide, long-acting natriuretic peptide, vessel dilator and ANF at their 10(-11) M concentrations inhibited Na(+)-K(+)-ATPase 39.5%, 27.8%, 19.2%, and 4% respectively, in bovine renal medulla, whereas their inhibition in renal cortical membranes was 37.5%, 27.5%, 20%, and 0%, respectively. Ouabain (0.5 mM) inhibited kidney medullary Na(+)-K(+)-ATPase 45% and in the cortex, 38%. There was no additive effect of any of these peptides with ouabain suggesting that they are interacting with the same site on the Na(+)-K(+)-ATPase as ouabain. To help elucidate the mechanism of these peptides' interaction with Na(+)-K(+)-ATPase, naproxen (0.5 mM), an inhibitor of prostaglandin synthesis, and direct measurement of prostaglandin E2 by RIA were used. Naproxen completely blocked the inhibition of Na(+)-K(+)-ATPase by kaliuretic peptide, long-acting natriuretic peptide, and vessel dilator suggesting that their inhibition of Na(+)-K(+)-ATPase in both the kidney medulla and cortex are mediated by prostaglandins. Direct measurement of prostaglandin E2 revealed that kaliuretic peptide > long-acting natriuretic peptide > vessel dilator increased prostaglandin E2 synthesis, whereas ANF did not have any effect. Of interest, angiotensin II and ouabain inhibition of Na(+)-K(+)-ATPase were also completely blocked by naproxen.     

The Na(+)-K(+)-ATPase beta 1 subunit is associated with the HK alpha 2 protein in the rat kidney

The Na-K-ATPase beta 1 subunit acts as the beta subunit for the HK alpha 2 protein in the rat kidney. The colonic H(+)-K(+)-ATPase is a member of the P-type ATPases, and has been shown to contribute to potassium transport by the mammalian kidney and colon. The P-type ATPases often consist of an alpha subunit that contains the catalytic site and a beta subunit that participates in regulation of enzyme activity and targeting of the enzyme to the plasma membrane. The cDNA of the alpha subunit (HK alpha 2) has been cloned and the HK alpha 2 protein has been isolated from the rat kidney and colon. However, a unique beta subunit for the colonic H(+)-K(+)-ATPase has not been described. To determine if one of the known beta subunits present in the kidney might act as the beta subunit for the colonic H(+)-K(+)-ATPase, microsomes enriched in the colonic H(+)-K(+)-ATPase were isolated using an HK alpha 2-specific antibody (AS 31.7) and the Minimac magnetic separation system. Immunoblots of rat kidney microsomal protein isolated with antibody AS 31.7 were probed with antibodies directed against the gastric HK beta subunit, Na(+)-K(+)-ATPase alpha 1, and Na(+)-K(+)-ATPase beta 1 subunits. A band of the appropriate size was detected with Na(+)-K(+)-ATPase beta 1-specific antibodies, but not those directed against HK beta 1. These data suggest that Na(+)-K(+)-ATPase beta 1 could be the beta subunit for the colonic H(+)-K(+)-ATPase in the kidney.     

Effect of aging on the activities of acetylcholinesterase, Na+,K(+)-ATPase and Mg(2+)-ATPase in rat pituitary and hypothalamus

Acetylcholinesterase (AChE), Na+,K(+)-ATPase and Mg(2+)-ATPase activities were estimated in homogenised rat pituitary and hypothalamus of 4- and 22-month-old rats. AChE activity was not altered in the pituitary of aged compared to adult rats, while it was found decreased by about 40% in the hypothalamus. Na+,K(+)-ATPase activity remained stable in the hypothalamus, while it was decreased by about 38% in the pituitary. Mg(2+)-ATPase activity remained unchanged in the hypothalamus, but was increased by about 83% in the pituitary. This pituitary Na+,K(+)-ATPase inactivation may result in pathological mood and decreased neural excitability and metabolic energy production in aged animals. The age-related alterations of AChE, Na+,K(+)-ATPase and Mg(2+)-ATPase activities may reflect changes in secretion and responses of some hormones of pituitary and hypothalamus.     

Plasma triglycerides cosegregate with erythrocyte sodium content in F2 rats of HTG x Lewis cross

The possible association of plasma lipids (triglycerides and cholesterol) with erythrocyte Na+ content (Na+i) and/or with alterations in red cell Na+ and K+ (Rb+) transport was studied in a population of F2 hybrids obtained by crossing hypertensive Prague hereditary hypertriglyceridaemic (HTG) rats with normotensive Lewis rats. The obtained data indicated a strong cosegregation (p < 0.001) of plasma triglycerides with erythrocyte Na+ content. This was the cause for the close correlation of plasma triglycerides with the Na(+)-K+ pump activity (measured as ouabain-sensitive Na+ extrusion). On the contrary, there was only marginal association (p < 0.05) of erythrocyte Na+ content with plasma cholesterol which was significantly (p < 0.01) related to burnetanide-sensitive Rb+ uptake mediated by the Na(+)-K+ cotransport system. Na+ leak (bumetanide-resistant net Na+ uptake) correlated positively with blood pressure in female but not in male F2 rats. The close association between plasma triglycerides and erythrocyte Na+ content suggests that ion transport alterations might contribute to mechanisms responsible for the cosegregation of blood pressure with plasma triglycerides in HTG x Lewis F2 hybrids.     

K+ fluxes mediated by Na(+)-K(+)-Cl- cotransport and Na(+)-K(+)-ATPase pumps in renal tubule cell lines transformed by wild-type and temperature-sensitive strains of Simian virus 40

The relative contributions of Na(+)-K(+)-ATPase pumps and Na(+)-K(+)-Cl- cotransport to total rubidium (Rb+) influx into primary cultures of renal tubule cells (PC.RC) and cells transformed either with the wild-type or a temperature-sensitive mutant of the simian virus 40 (SV40), were measured under various growth conditions. The Na(+)-K(+)-ATPase-mediated component represented 74% and 44-48% of total Rb+ influx into PC.RC and SV40-transformed cells, respectively. Proliferating transformed cells showed substantial ouabain-resistant bumetanide-sensitive (Or-Bs) Rb+ influx (41-45% of total) which indicated the presence of a Na(+)-K(+)-Cl- cotransport. The Or-Bs component of Rb+ influx was greatly reduced when temperature-sensitive transformed renal cells (RC.SVtsA58) grown in Petri dishes or on permeable filters were shifted from the permissive (33 degrees C) to the restrictive temperature (39.5 degrees C) to arrest cell growth. The ouabain-sensitive Rb+ influx mediated by the Na(+)-K(+)-ATPase, the total and amiloride-sensitive Na+ uptakes were not modified following inhibition of cell proliferation. A similar fall in the Or-Bs influx was obtained when renal tubule cells transformed by the wild-type SV40 (RC.SV) were incubated with the K+ channel blocker, tetraethylammonium (TEA) ion, which we had previously shown to arrest cell growth without affecting cell viability (Teulon et al.: J. Cell. Physiol., 151:113-125, 1992). Reinitiation of cell growth by removal of TEA or return to 33 degrees C of the temperature-sensitive cells restored the Or-Bs component of Rb influx. Taken together, these results indicate that the Na(+)-K(+)-Cl- cotransport activity is critically dependent on cell growth conditions.     

Reduced Na(+)-K(+)-ATPase activity and plasma lysophosphatidylcholine concentrations in diabetic patients

A fraction from normal human plasma inhibiting Na(+)-K(+)-ATPase has been recently identified as lysophosphatidylcholine (LPC). The aim of this study was to investigate the existence of a relationship between the activity of the cellular membrane Na(+)-K(+)-ATPase and plasma LPC in human diabetes. We studied 10 patients with insulin-dependent-diabetes mellitus (IDDM), 14 patients with non-insulin-dependent diabetes mellitus (NIDDM), and 10 sex- and age-matched control subjects. Plasma LPC concentrations were increased in both IDDM and NIDDM patients compared with control subjects. Na(+)-K(+)-ATPase activity was reduced in both groups of patients in erythrocyte and platelet membranes. There was a significant correlation between the concentrations of plasma LPC and Na(+)-K(+)-ATPase activity in both erythrocyte and platelet membranes (P < 0.01). To investigate the effect of LPC on the enzyme, Na(+)-K(+)-ATPase activity was determined in erythrocyte membranes obtained from six healthy subjects after in vitro incubation with increasing concentrations of LPC (1-10 microM). Enzymatic activity was significantly reduced by in vitro LPC at a concentration of 2.5 microM, with a further decrease at 5 microM. These data suggest that the decrease in Na(+)-K(+)-ATPase activity in diabetes might be due to increased LPC concentrations.