Correlation between secretagogue-induced Ca2+ influx, intracellular Ca2+ levels and secretion of catecholamines in cultured adrenal chromaffin cells

BACKGROUND: Complex branched muscle fibers are frequently observed in the muscles of mdx mutant mice and/or in damaged muscles. To investigate whether the complex branched fibers were present in the compensatory hypertrophied muscles of rats, we examined the morphological changes in these muscles. METHODS: We examined the hypertrophied plantaris (PLA) muscle of the Wistar male rats, prepared by surgical ablation of synergistic muscles. The muscle was examined using three-dimensional analysis with scanning electron microscopy, immunohistochemical detection of proliferating cells using 5-bromo-2'-deoxyuridine (BrdU) and histological and histochemical characterization. Studies were performed at 48 hours, 2, 4, 6, 10, and 15 weeks after surgical preparation. RESULTS: The muscle hypertrophy ratio (muscle weight relative to the contralateral intact control side), gradually increased from 2 to 10 weeks, and the peak value (48.6%) occurred at the 10th week. The total number of fibers did not change significantly at any time interval. However, the number of branched muscle fibers increased significantly (P < 0.05) after 6 weeks, and accounted for about 2.5% of the total fibers at the 15th week. Most branched fibers showed complex features resembling the "anastomosing syncytial reticulum" described in myopathic animals. The fibers were observed mainly in the middle and distal portions of the PLA muscle. The proportion and distribution of proliferating cells in the entire PLA muscle corresponded with the distribution of the complex branched fibers. These results were also observed in muscle tissues prepared for histological and histochemical examination. CONCLUSIONS: The presence of a large proportion of complex branched fibers in a limited segment of the compensatory hypertrophied muscle suggests that this hypertrophy model represents a pathological and/or pathophysiological hypertrophy model rather than a normal physiological process.     

Mechanism of nitric oxide-induced vasodilatation: refilling of intracellular stores by sarcoplasmic reticulum Ca2+ ATPase and inhibition of store-operated Ca2+ influx

The precise mechanisms by which nitric oxide (NO) decreases free [Ca2+]i, inhibits Ca2+ influx, and relaxes vascular smooth muscle are poorly understood. In rabbit and mouse aorta, agonist-induced contractions and increases in [Ca2+]i were resistant to nifedipine, suggesting Ca2+ entry through non-L-type Ca2+ channels. Relaxations to NO were inhibited by thapsigargin (TG) or cyclopiazonic acid (CPA) indicating the involvement of sarcoplasmic reticulum ATPase (SERCA). Studies of the effect of NO on [Ca2+]i and the rate of Mn2+ influx with fura-2 fluorometry in rabbit aortic smooth muscle cells in primary culture were designed to test how SERCA is involved in mediating the response to NO. When cells were stimulated with angiotensin II (AII), NO accelerated the removal of Ca2+ from the cytoplasm, decreased [Ca2+]i, and inhibited Ca2+ and Mn2+ influx. Inhibition of SERCA abolished all the effects of NO. In contrast, inhibition of the Na+/Ca2+exchanger or the plasma membrane Ca2+ ATPase had no influence on the ability of NO to decrease [Ca2+]i. NO maximally decreased [Ca2+]i within 5 s, whereas significant inhibition of AII-induced Ca2+ and Mn2+ influx required more than 15 s. The inhibition of cation influx strictly depended on [Ca2+]o and functional SERCA, suggesting that during the delay before NO inhibits Ca2+ influx, the influx of Ca2+ and the uptake into intracellular stores are required. In the absence of [Ca2+]o, NO diminished the AII-induced [Ca2+]i transient by a SERCA-dependent mechanism and increased the amount of Ca2+ in the stores subsequently released by ionomycin. The present study indicates that the initial rapid decrease in [Ca2+]i caused by NO in vascular smooth muscle is accounted for by the uptake of Ca2+ by SERCA into intracellular stores. It is proposed that the refilling of the stores inhibits store-operated Ca2+ influx through non-L-type Ca2+ conducting ion channels and that this maintains the decrease in [Ca2+]i and NO-induced relaxation.     

Inositol trisphosphate receptors: Ca2+-modulated intracellular Ca2+ channels

The three subtypes of inositol trisphosphate (InsP3) receptor expressed in mammalian cells are each capable of forming intracellular Ca2+ channels that are regulated by both InsP3 and cytosolic Ca2+. The InsP3 receptors of many, though perhaps not all, tissues are biphasically regulated by cytosolic Ca2+: a rapid stimulation of the receptors by modest increases in Ca2+ concentration is followed by a slower inhibition at higher Ca2+ concentrations. Despite the widespread occurrence of this form of regulation and the belief that it is an important element of the mechanisms responsible for the complex Ca2+ signals evoked by physiological stimuli, the underlying mechanisms are not understood. Both accessory proteins and Ca2+-binding sites on InsP3 receptors themselves have been proposed to mediate the effects of cytosolic Ca2+ on InsP3 receptor function, but the evidence is equivocal. The effects of cytosolic Ca2+ on InsP3 binding and channel opening, and the possible means whereby the effects are mediated are discussed in this review.     

Increase of intracellular Ca2+ and relocation of E-cadherin during experimental decompaction of mouse embryos

To determine the role of intracellular Ca2+ in compaction, the first morphogenetic event in embryogenesis, we analyzed preimplantation mouse embryos under several decompacting conditions, including depletion of extracellular Ca2+, blocking of Ca2+ channels, and inhibition of microfilaments, calmodulin, and intracellular Ca2+ release. Those treatments induced decompaction of mouse morulae and simultaneously induced changes in cytosolic free Ca2+ concentration and deregionalization of E-cadherin and fodrin. When morulae were allowed to recompact, the location of both proteins recovered. In contrast, actin did not change its cortical location with compaction nor with decompaction-recompaction. Calmodulin localized in areas opposite to cell-cell contacts in eight-cell stage embryos before and after compaction. Inhibition of calmodulin with trifluoperazine induced its delocalization while morulae decompacted. A nonspecific rise of intracellular free Ca2+ provoked by ionomycin did not affect the compacted shape. Moreover, the same decompacting treatments when applied to uncompacted embryos did not produce any change in intracellular Ca2+. Our results demonstrate that in preimplantation mouse embryos experimentally induced stage-specific changes of cell shape are accompanied by changes of intracellular free Ca2+ and redistribution of the cytoskeleton-related proteins E-cadherin, fodrin, and calmodulin. We conclude that intracellular Ca2+ specifically is involved in compaction and probably regulates the function and localization of cytoskeleton elements.     

P2u purinoceptor modulation of intracellular Ca2+ in a human lung adenocarcinoma cell line: down-regulation of Ca2+ influx by protein kinase C

The aim of the present investigation was to study the functional alterations in the stomatognathic system following orthodontic-surgical management of skeletal vertical excess problems. The sample comprised 43 patients who received combined orthodontic-surgical treatment including bilateral vertical ramus osteotomy for posterior repositioning and counterclockwise rotation of the mandible (n = 26) or Le Fort I osteotomy for maxillary impaction (n = 17). All subjects were examined within 1 week before operation and 6 months postsurgery. Methods of examination included: (a) evaluation of dysfunction by means of a clinical index, (b) measurement of mandibular range of motion, (c) assessment of the number and intensity of occlusal contacts, and (d) tomographic evaluation of condyle-fossa relationships. The results of the study indicated that postoperatively (a) there was an increase of patients with dysfunction in the mandibular osteotomy group and a decrease of patients with dysfunction in the maxillary osteotomy group; (b) the maximum interincisal opening decreased significantly in the mandibular osteotomy group; (c) there was a significant increase in the number and intensity of occlusal contacts in both groups; and (d) the shortest posterior and anterior interarticular distances increased significantly in the mandibular osteotomy group.     

Cyclopiazonic acid and thapsigargin induce platelet aggregation resulting from Ca2+ influx through Ca2+ store-activated Ca2+-channels

The effects of cyclopiazonic acid and thapsigargin, selective inhibitors of the endoplasmic reticulum Ca2+-ATPase pump, on the platelet aggregation were investigated using washed rat platelets prepared by chromatography on Sepharose 2B columns. In Ca2+-free medium, cyclopiazonic acid and thapsigargin did not induce aggregation, but in the presence of 1 mM Ca2+, platelet aggregation was induced in a concentration-dependent manner. Cyclopiazonic acid- and thapsigargin-induced platelet aggregation was blocked by 1 mM Ni2+ but not by 100 microM indomethacin or 1 microM nifedipine. In aequorin-loaded platelets, cyclopiazonic acid and thapsigargin caused sustained elevation of the cytosolic Ca2+ concentration, an effect which was blocked by Ni2+, a non-selective Ca2+ channel blocker and SK&F 96365 (1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenyl]-1H-imidazole hydrochloride), a putative receptor-operated Ca2+ channel antagonist. The above results indicated that both cyclopiazonic acid and thapsigargin induced platelet aggregation and elevation of cytosolic Ca2+ concentration, that extracellular Ca2+ was essential for cyclopiazonic acid- and thapsigargin-induced platelet aggregation, and that platelet aggregation may be associated with Ca2+ influx through Ca2+ store-activated Ca2+ channels.     

Dual effect of the anti-allergic astemizole on Ca2+ fluxes in rat basophilic leukemia (RBL-2H3) cells: release of Ca2+ from intracellular stores and inhibition of Ca2+ release-activated Ca2+ influx

The antiallergic drugs astemizole and norastemizole inhibit exocytosis in mast cells, which might be relevant for their therapeutic action. From previous studies, it appeared that the drugs inhibited 45Ca2+ influx. Here, we present a more detailed study on the effects of astemizole and norastemizole on Ca2+ fluxes. Fura-2-loaded rat basophilic leukemia (RBL-2H3) cells were activated through the high-affinity receptor for IgE (FcepsilonRI) with antigen or by the endoplasmatic reticulum ATPase inhibitor thapsigargin, bypassing direct FcepsilonRI-related events. It appeared that astemizole (>15 microM), in contrast to norastemizole, showed a dual effect on intracellular calcium concentration ([Ca2+]i): a rise in intracellular calcium concentration was induced, which originated in the release of intracellular Ca2+ stores, whereas Ca2+ influx via store-operated Ca2+ (SOC) channels was inhibited. Ca2+ influx was further characterized using Ba2+ influx, whereas processes in the absence of Ca2+ influx were studied using Ni2+ or EGTA. It was concluded that the drugs most likely affect the store-operated Ca2+ channels in RBL cells directly. The two effects of astemizole on Ca2+ fluxes had opposing influences on exocytosis, thereby accounting for the biphasic effect of increasing astemizole concentration on mediator release in RBL cells.     

Increased intracellular Ca2+ signaling caused by the antitumor agent helenalin and its analogues

The antitumor sesquiterpene lactone helenalin, which is found in species of the plant genus Helenium, caused a marked potentiation of the increases in intracellular free Ca2+ concentration ([Ca2+]i) produced by mitogens such as vasopressin, bradykinin, and platelet-derived growth factor in Swiss mouse 3T3 fibroblasts. Removing external Ca2+ partly attenuated the increased [Ca2+]i responses caused by helenalin. The increased [Ca2+]i responses occurred at concentrations of helenalin that inhibited cell proliferation. At higher concentrations, helenalin inhibited the [Ca2+]i responses. No change in resting [Ca2+]i was caused by helenalin even at high concentrations. Other helenalin analogues also increased the [Ca2+]i response. Helenalin did not inhibit protein kinase C (PKC) and PKC appeared to play a minor role in the effects of helenalin on [Ca2+]i responses in intact cells. Studies with saponin-permeabilized HT-29 human colon carcinosarcoma cells indicated that helenalin caused an increased accumulation of Ca2+ into nonmitochondrial stores and that the potentiating effect of helenalin on mitogen-stimulated [Ca2+]i responses was due in part to an increase in the inositol-(1,4,5)-trisphosphate-mediated release of Ca2+ from these stores.     

Ca2+ influx activated by low pH in Chlamydomonas

Cytosolic acidification stimulates an influx of Ca2+ which results in shedding of the two flagella of Chlamydomonas. Ca2+ influxes are also involved in the photoresponses of this alga, but it is not understood how the acidification-activated Ca2+ influx is distinguished from the Ca2+ influxes which mediate phototaxis and the photophobic response. The present study focuses on the deflagellation-inducing Ca2+ influx pathway. Influx occurs through an ion channel or transporter with low abundance or low permeability to Ca2+ (approximately 500 fmol/s/10(6) cells in 50 microM Ca2+). Ca2+ influx was potently blocked by Cd3+ (EC50 approximately 5 microM), but was insensitive to Cd2+ (Quarmby, L.M., and H.C. Hartzell. 1994. J. Cell Biol. 124:807) and organic blockers of Ca2+ channels including SKF-96365 (up to 100 microM) and flufenamic acid (up to 1 mM). Experiments with a flagella-less mutant (bald-2), isolated flagella, and a blocker of flagellar assembly (colchicine) indicated that the acidification-stimulated Ca2+ influx pathway is not localized to the flagellar membrane. The acid-stimulated influx pathway was transiently inactivated after cells shed their flagella. Inactivation did not occur in the deflagellation mutant, fa-1, although acidification-stimulated Ca2+ influx was normal. This suggests that inactivation of this pathway in wild-type cells is probably not a direct consequence of acidification nor of Ca2+ influx, but may be related to deflagellation. Recovery of deflagellation-inducing Ca2+ influx occurred within 30 min after a 30 s exposure to acid and did not require flagellar assembly. The regulation, drug sensitivity, and subcellular localization identify acidification-stimulated Ca2+ influx as a specific Ca2+ entry pathway distinct from established Ca2+ channels.     

Non-ionophoretic elevation of intracellular Ca2+ by Lonidamine

Lonidamine is an antispermatogenic and anticancer drug that is believed to act by inhibition of energy metabolism. In this study, the effects of Lonidamine on the concentration of intracellular free Ca2+ of several tumor cell lines were assessed because of the important role that cytosolic Ca2+ plays in cell viability and proliferation. The presence of 300 microM Lonidamine resulted in large elevations of cytosolic Ca2+ (> 100 nM) in AS-30D rat ascites hepatoma cells and in cultured EMT6 murine mammary adenocarcinoma cells but had little effect on cultured NCI-H345 human small cell lung cancer cells. The apparent EC50 for Lonidamine was approximately 175 microM. The source of elevated cytosolic Ca2+ was primarily intracellular stores, and the effects of Lonidamine on Ca2+ efflux from these stores did not appear to be due to an ionophoretic action of this compound or to a decline in the level of cellular ATP. These results indicate that the Ca2+ homeostasis of certain lines of tumor cells is specifically altered by Lonidamine at concentrations known to affect cell proliferation.     

Pituitary adenylate cyclase-activating polypeptide causes rapid Ca2+ release from intracellular stores and long lasting Ca2+ influx mediated by Na+ influx-dependent membrane depolarization in bovine adrenal chromaffin cells

Pituitary adenylate cyclase-activating polypeptide (PACAP) has been reported to increase intracellular Ca2+ concentrations ([Ca2+]i) and catecholamine release in adrenal chromaffin cells. We measured [Ca2+]i with fura-2 and recorded ion currents and membrane potentials with the whole cell configuration of the patch-clamp technique to elucidate the mechanism of PACAP-induced [Ca2+]i increase in bovine adrenal chromaffin cells. PACAP caused [Ca2+]i to increase due to Ca2+ release and Ca2+ influx, and this was accompanied by membrane depolarization and inward currents. The Ca2+ release was suppressed by ryanodine, an inhibitor of caffeine-sensitive Ca2+ stores, but was unaffected by cinnarizine, an inhibitor of inositol trisphosphate-induced Ca2+ release. Ca2+ influx and inward currents were both inhibited by replacement of extracellular Na+, and Ca2+ influx was inhibited by nicardipine, an L-type Ca2+ channel blocker, or by staurosporine, a protein kinase C (PKC) inhibitor, but was unaffected by a combination of omega- conotoxin-GVIA, omega-agatoxin-IVA, and omega-conotoxin- MVIIC, blockers of N-, P-, and Q-type Ca2+ channels. Moreover, 1-oleoyl-2-acetyl-sn-glycerol, a PKC activator, induced inward currents and Ca2+ influx. These results indicate that PACAP causes both Ca2+ release, mainly from caffeine-sensitive Ca2+ stores, and Ca2+ influx via L-type Ca2+ channels activated by membrane depolarization that depends on PKC-mediated Na+ influx.     

Canine bronchial sustained contraction in Ca2+-free medium: role of intracellular Ca2+

We evaluated whether cartilage was a source of Ca2+ and the possible role of Ca2+ recycling in the sustained bronchial contraction (SBC) induced by carbachol (Cch) in Ca2+-free medium. Canine first-order bronchi were studied with cartilage and epithelium (+CAR + EPI) and without these structures individually (-CAR + EPI and +CAR - EPI) or together (-CAR - EPI). After cartilage removal (-CAR - EPI or -CAR + EPI) Cch produced a transient contraction in Ca2+-free medium. Removal of the epithelium alone had minor effects on the magnitude of the SBC but increased the effect of removal of cartilage to diminish the SBC. Bronchial strips with cartilage were able to respond to Cch with lower Ca2+ concentrations (10-100 microM) than could dissected preparations. Preincubation with BAY K 8644 (30-1000 nM) or 60 mM KCl or -CAR - EPI tissues converted the transient contractions to Cch in Ca2+-free medium to sustained contractions. In microelectrode studies, 50 nM Cch induced membrane oscillations in solutions with 2.5 mM Ca2+ in bronchial preparations, plus or minus cartilage, and in undissected tissues in Ca2+-free medium but not in -CAR - EPI tissues. Preincubation with 1 microM BAY K 8644 in Ca(2+)-free medium restored these oscillations in -CAR - EPI tissues. The release of 45Ca2+ from cartilage was too rapid to provide a reservoir of Ca2+ to support multiple SBCs in Ca2+-free medium. Moreover, in the Ca2+-free medium (with 10 nM Ca2+ after tissue +CAR + EPI incubation) excitatory junction potentials rapidly disappeared. Addition of 1 microM nifedipine or 1 mM EGTA during the SBC of +CAR + EPI tissues produced complete relaxation. A transient contraction to Cch occurred with prior addition of nifedipine. Inhibition of the sarcoplasmic reticulum Ca2+ pump by tissue incubation with cyclopiazonic acid (CPA; 10 microM), or briefly with 1 mM EGTA significantly diminished the SBC induced by Cch in Ca2+-free medium. CPA and EGTA together abolished the Cch-induced SBC. Thus, cartilage plays a more complex role than as a Ca2+ reservoir to support the SBC induced by Cch in Ca2+-free solution; its removal affects the process supporting SBCs involving intracellular Ca2+ storage and Ca2+ entrance through voltage-dependent channels.     

Stimulation by DIF causes an increase of intracellular Ca2+ in Dictyostelium discoideum

Using fluorescence-activated cell sorting (FACS), we have studied the effect of the differentiation-inducing factor (DIF) on cellular Ca2+ in Dictyostelium discoideum. We have shown previously that freshly starved or postaggregation amoebae are heterogenous with respect to the amounts of cellular Ca2+ that they contain; the L or "low Ca2+" class exhibits a prespore tendency and the H or "high Ca2+" class exhibits a prestalk tendency. Upon adding DIF, within 2 min there is an approximately twofold increase in the relative fraction of amoebae falling in the H class. A major part of the increase is caused by Ca2+ influx from the extracellular medium. Therefore a rise in the level of cellular Ca2+ is an early step in the signal transduction pathway following stimulation by DIF. Also, in parallel with the cellular heterogeneity in respect of Ca2+ content, there is a heterogeneity in the response to DIF, which appears to be restricted to L cells.     

Role of Ca2+/K+ ion exchange in intracellular storage and release of Ca2+

Although fluctuations in cytosolic Ca2+ concentration have a crucial role in relaying intracellular messages in the cell, the dynamics of Ca2+ storage in and release from intracellular sequestering compartments remains poorly understood. The rapid release of stored Ca2+ requires large concentration gradients that had been thought to result from low-affinity buffering of Ca2+ by the polyanionic matrices within Ca2+-sequestering organelles. However, our results here show that resting luminal free Ca2+ concentration inside the endoplasmic reticulum and in the mucin granules remains at low levels (20-35 microM). But after stimulation, the free luminal [Ca2+] increases, undergoing large oscillations, leading to corresponding oscillations of Ca2+ release to the cytosol. These remarkable dynamics of luminal [Ca2+] result from a fast and highly cooperative Ca2+/K+ ion-exchange process rather than from Ca2+ transport into the lumen. This common paradigm for Ca2+ storage and release, found in two different Ca2+-sequestering organelles, requires the functional interaction of three molecular components: a polyanionic matrix that functions as a Ca2+/K+ ion exchanger, and two Ca2+-sensitive channels, one to import K+ into the Ca2+-sequestering compartments, the other to release Ca2+ to the cytosol.     

Diisopropyl fluorophosphate inhibits receptor-activated Ca2+ influx in isolated rat hepatocytes

The influence of diisopropyl fluorophosphate (DFP) on receptor-activated increases in cytosolic free Ca2+ concentration ([Ca2+]i) in isolated rat hepatocytes was monitored by measuring phosphorylase a activity and the fluorescence ratio of the Ca2+ sensitive dye Indo-1. Pretreatment (2 min) of hepatocytes with DFP (1 mM) inhibited maximal increases in phosphorylase a activity stimulated by phenylephrine (1 microM), angiotensin II (5 nM), or vasopressin (10 nM) by 36, 35, and 17%, respectively, when the cells were incubated in Ca2+ (1 mM)-containing medium. In contrast, agonist-stimulated increases in phosphorylase a activity were similar in control and DFP-pretreated cells when cells were incubated in medium containing very low (10 nM) Ca2+. Addition of Ca2+ (1 mM) to hepatocytes maintained in the low Ca2+ buffer and exposed to agonists rapidly increased phosphorylase a activity in control cells; however, increases in DFP-pretreated cells were markedly attenuated. Changes in [Ca2+]i similar to those noted with phosphorylase a were observed using Indo-1. Addition of calcium ionophore A23187 to control or DFP-pretreated hepatocytes increased phosphorylase a activity to a similar extent in control and DFP-pretreated cells, demonstrating that DFP pretreatment did not alter the ability of the enzyme to respond to elevation in [Ca2+]i. Collectively, these data indicate that DFP pretreatment of hepatocytes irreversibly inhibits one or more components of the Ca2+ influx pathway.     

Melatonin inhibits GnRH-induced Ca2+ mobilization and influx through voltage-regulated channels

In neonatal rat gonadotrophs, melatonin acts through the high-affinity membrane-bound receptors to inhibit GnRH-induced [Ca2+]i increase. GnRH increases [Ca2+]i primarily by mobilization from the inositol trisphosphate-sensitive pool followed by Ca2+ influx through the voltage-sensitive channels. Melatonin inhibits the GnRH-induced [Ca2+]i increase. When added after the GnRH-induced spike, melatonin decreases [Ca2+]i in 52% of the gonadotrophs. The effect of melatonin is dependent on extracellular Ca2+ and may be mimicked by Ca2+-free medium or verapamil. When added before GnRH, melatonin inhibits the [Ca2+]i spike. This effect of melatonin is independent of extracellular Ca2+ as it persists in Ca2+-free medium. These findings indicate that melatonin blocks Ca2+ mobilization as well as Ca2+ influx in the gonadotrophs.     

ATP, thapsigargin and cAMP increase Ca2+ in rat hepatocytes by activating three different Ca2+ influx pathways

OBJECTIVE: To evaluate the risk and efficacy of pulmonary lobectomy in dogs with pneumonia. DESIGN: Retrospective study. ANIMALS: 59 dogs with pneumonia. PROCEDURE: Review of medical records and telephone conversations. RESULTS: 54.2% of dogs had resolution of pneumonia after lobectomy, 20.3% died in the perioperative period, and 25.4% survived the perioperative period but pneumonia did not resolve. Pneumonia was caused by bacteria (25 dogs), fungi (12), foreign bodies (8), parasites (1), viruses (1), and allergies (1). In 11 dogs, the etiologic agent was not isolated. Bacterial or fungal pneumonias were significantly less likely to resolve compared with foreign body pneumonia or when an etiologic agent was not isolated. Perioperative mortality rate increased significantly with an increase in number of pulmonary lobes removed. Complications during surgery significantly increased perioperative mortality rate. Surgical era (1972 to 1983 vs 1984 to 1994) was a significant predictor of mortality, with the odds of dying in the perioperative period being 11 times greater between 1972 to 1983. The odds of failure to resolve pneumonia was 3 times greater during 1972 to 1983. CLINICAL IMPLICATIONS: Number of pulmonary lobes removed and complications during surgery significantly affect perioperative mortality rate. Identification of etiologic agents may help in predicting dogs likely to resolve pneumonia after surgery.     

Role of calreticulin in regulating intracellular Ca2+ storage and capacitative Ca2+ entry in HeLa cells

Protein and energy metabolism in boars of different breeds, 10 each of Hampshire, Duroc and Danish Landrace was measured in balance and respiration experiments by means of indirect calorimetry in an open-air circulation system. Measurements were performed in four periods (Period I-IV) covering the body weight range from 25 to 100 kg. In order to achieve maximum protein retention (RP) a daily intake of digestible protein > 12 g/kg0.75 and metabolisable energy > 1100 kJ/kg0.75 was assumed to be necessary. Protein retention of Danish Landrace boars was inferior to that of Hampshire and Duroc boars in Periods III and IV, and therefore, 55 measurements on Hampshire and Duroc boars fulfilling the chosen criteria for digested protein and ME intake were used for calculation of maximum protein retention, giving the following significant quadratic relationship: RP [g/d] = 11.43.W0.75-0.144.W1.50 (n = 55, RSD = 15.2, CV = 9.2%, R2 = 0.851) with a summit of 227 g/d at 135 kg BW. In Period I, when BW was below 30 kg, 12 measurements fulfilled the chosen criterion for digested protein but not for ME, and these data were used comparatively. Protein retention of boars with a low ME intake in Period I was significantly below that of boars with a high ME intake (93 g/d vs. 107 g/d; P = 0.02). In summary, the present data have shown that boars of high genetic potential have capacity for maximum protein retention of about 230 g/d, and that there was a significant quadratic relationship between protein retention and metabolic body weight, indicating that maximum protein retention was not reached until 135 kg BW. Differences in capacity for protein retention were recorded between boars of different breeds, with Duroc and Hampshire boars being superior to Danish Landrace boars. Additionally, the crucial importance of a sufficient ME supply early in the growth period was underscored by a lower protein accretion rate of boars given a daily ME supply below 1100 kJ ME/kg0.75 at an approximate BW of 25 kg.     

Histamine H1-receptors in HL-60 monocytes are coupled to Gi-proteins and pertussis toxin-insensitive G-proteins and mediate activation of Ca2+ influx without concomitant Ca2+ mobilization from intracellular stores

The responses of renal haemodynamic and natriuretic indices to the oral prostaglandin synthetase inhibitor indomethacin (200 mg), to infused angiotensin II (1 ng min-1 kg-1) and to the combination of the two were studies in placebo-controlled fashion in eight normal male subjects both prior to and following administration of intravenous frusemide (20 mg). As compared with placebo, angiotensin II infusion alone caused significant reductions in absolute rate of sodium excretion, fractional sodium excretion, urine flow rate and effective renal plasma flow (all P < 0.001 vs placebo) but had no effect on glomerular filtration rate. The only change observed in these parameters with indomethacin alone was a small but significant reduction in urine flow rate (P < 0.005 vs placebo). As compared with the effects of angiotensin II alone, indomethacin pre-treatment followed by angiotensin II infusion led to much greater falls in absolute rate of sodium excretion, fractional sodium excretion, urine flow rate and effective renal plasma flow (all P < 0.0001 vs placebo) associated with a significant reduction in glomerular filtration rate (P < 0.0001) not observed with angiotensin II alone. Frusemide administration at the midpoint of each study limb resulted in each case in a prompt 15 to 20 fold increase in natriuresis. The renal haemodynamic and natriuretic effects of angiotensin II, indomethacin and their combination were not qualitatively different from those observed in the pre-frusemide phase. Our findings provide a clear demonstration in man of the important homeostatic role of renal prostaglandins in preserving renal function, particularly glomerular filtration, under conditions of elevated circulating angiotensin II.