Protein kinase C mediates flow-induced prostaglandin E2 production in osteoblasts

A study was conducted, on 30 human fetuses, of the structures passing through the tympanosquamosal fissure. The tympanosquamosal fissure lies between the middle ear and the temporomandibular region. Meckel's cartilage passes through the tympanosquamosal fissure and continues on into the middle ear with the cartilaginous anlage of the malleus. A tract of fibrous tissue arises from the mesenchyme, located cranial and lateral to Meckel's cartilage, that enters from the posterior area of the temporomandibular joint disc to the middle ear through the tympanosquamosal fissure, and attaches onto the area of continuity of Meckel's cartilage with the malleus. Transformation of Meckel's cartilage into the sphenomandibular ligament and anterior ligament of the malleus determines their continuity through the tympanosquamosal fissure. The posterior fibers of the temporomandibular joint disc giving rise to the discomalleolar ligament insert into the anterior ligament of the malleus.     

Long-term shake suspension and membrane vesicles of medullary thick ascending limb

We investigated the effects of stress over the final stages of sexual maturation on the reproductive performance of female rainbow trout, Oncorhynchus mykiss. Stress was administered over the period of early vitellogenesis (1.5 mo), late vitellogenesis-final maturation (1.5 mo), or during both periods (3 mo). Each stress treatment and control was triplicated, with eight females in each replicate (n = 24 fish per treatment). The eggs and progeny of each female were kept separate, and observations were made for 4 mo after transfer to rearing tanks. Fish that experienced stress during final maturation and those that were under stress during the whole experiment ovulated on average 2 wk earlier than the control group. In contrast, fish stressed during the period of early vitellogenesis ovulated at the same time as controls. Absolute fecundity and fertilization were not significantly affected in any treatment group, but significant differences in relative fecundity were found. Stress applied early in vitellogenesis resulted in smaller eggs and swim-up fry. No significant differences were found in juvenile weight 8 wk after hatching. Furthermore, we found no differences in survival of the progeny or resistance to the fish pathogen Vibrio anguillarum. Thus, mild acute stresses applied to rainbow trout females may affect certain reproductive performance parameters such as timing of ovulation and relative fecundity; however, the progeny of such stressed females perform as well as controls with regard to juvenile growth and disease resistance.     

Macrophage-induced inhibition of nitric oxide production in primary rat hepatocyte cultures via prostaglandin E2 release

Kupffer cells and other macrophages play an important role in pathogenesis of toxicants in the liver. The aim of this study was to evaluate the effect of macrophages on hepatocyte production of nitric oxide (NO), which has been previously reported to be protective toward oxidative stress induced in primary rat hepatocytes. For this purpose, RAW 264.7 macrophages were added to primary rat hepatocytes at various ratios between macrophages and hepatocytes. These cocultures were supplemented with lipopolysaccharide (LPS) and interferon gamma (IFN-gamma) for 23 hours to induce NO synthase and trigger NO production. NO production was followed by quantification of nitrites in culture medium and dinitrosyl iron complexes (DNIC) in intact hepatocytes after separation from macrophages. In cocultured hepatocytes incubated with LPS and IFN-gamma, DNIC and nitrite levels decreased compared with those observed in hepatocytes cultured without macrophages in the same conditions. Moreover, inhibition of NO production in hepatocyte cocultures was macrophage-number-dependent. Macrophage-conditioned medium also inhibited NO production in hepatocytes, suggesting that the effect of macrophages was mediated by soluble factors. Among the soluble factors known to decrease NO levels are some cytokines, growth factors, reactive oxygen species, and prostaglandins. Ultrafiltration of macrophage-conditioned medium through a 500-d membrane to rule out higher-molecular-weight molecules, such as anti-inflammatory cytokines and growth factors, failed to restore NO production. In the same way, the use of superoxide dismutase (SOD) and catalase (CAT) to eliminate reactive oxygen species produced by macrophages did not lead to recovery of NO levels in hepatocytes. However, when NO synthesis was inhibited in macrophages by NG-monomethyl-L-arginine (L-NMMA), hepatocytes recovered the capacity to produce NO. A net decrease of prostaglandin E2 (PGE2) release by macrophages was concomitantly observed. Moreover, inhibition of PGE2 production in macrophages by indomethacin led to restoration of NO levels. Taken together, our observations suggest that NO synthesized by macrophages can decrease NO production in hepatocytes via PGE2 release. Because of the protective role of NO toward many liver injuries, it may be postulated that macrophages contribute through this mechanism to liver damage.     

Actions of prostaglandin E2 on rat supraoptic neurones

Prostaglandins (PGs) have been implicated in the regulation of vasopressin (VP) and oxytocin (OT) release in response to various stimuli. To examine the site and mechanism of actions of PGs, we studied effects of PGE2 and PG-receptor agonists on supraoptic nucleus (SON) neurones of rat hypothalamic slice preparations using extracellular recording and whole-cell patch-clamp techniques. PGE2 modulated the electrical activity of more than 80% of the neurones studied. The effects of PGE2 on both phasic and non-phasic neurones were mostly excitatory, and dose-dependent. The effects of PGE2 were mimicked by PGF2alpha or the FP agonist, fluprostenol, whereas PGD2 or the selective EP, IP or TP agonist was less effective or had no effect. The effects of PGE2 were unaffected by the EP1 antagonist, SC-51322, but reduced to 80% of control by the EP1/FP/TP antagonist, ONO-NT-012, which reduced the effects of fluprostenol to 32% of control. Moreover, some neurones responsive to PGE2 did not respond to fluprostenol. Patch-clamp analysis in SON slice preparations revealed that PGE2 at 10(-6) M depolarized the membrane potential by 3.9+/-0.3 mV from the resting membrane potential of -58.4+/-2.2 mV in the current-clamp mode. In the voltage-clamp mode, PGE2 induced inward currents at a holding potential of -70 or -80 mV, while it did not affect spontaneous excitatory postsynaptic currents. PGE2 induced currents also in dissociated SON neurones and the reversal potential of the currents was -35.5+/-0.9 mV, which was similar to that of currents induced by fluprostenol. These results suggest that SON neurones possess at least two types of PG receptors, FP receptors and EP receptors of a subclass different from EP1, EP2, or EP3, and that activation of these receptors leads to the opening of nonselective cation channels, membrane depolarization and increase of the action potential discharge.     

Calcium-sensing receptor: regulation of electrolyte transport in the thick ascending limb of Henle's loop

A calcium-sensing receptor (CaR) has functionally been described in the cortical thick ascending limb of Henle's loop (CTAL) of rat and mouse. This G protein-coupled receptor activates phospholipase C and increases the intracellular Ca2+ concentration. We observed that in the mouse CTAL cAMP formation, induced by 10(-8) mol/l AVP, was inhibited by more than 90% when the extracellular Ca2+ concentration ([Ca2+]e) was increased from 0.5 to 3 mmol/l. Measurements of transepithelial potential difference (PDte) in rat and mouse CTAL and medullary thick ascending limb (mTAL) segments and of transepithelial ion net fluxes in the mouse CTAL (isotonic perfusion conditions: 150 mmol/l NaCl in the lumen and bath) showed that an increase in the [Ca2+]e had no effect on basal and arginine vasopressin (AVP, 10(-10) mol/l)-stimulated transepithelial PDte, NaCl and Mg2+ transport. However, Ca2+ reabsorption was strongly inhibited by increased [Ca2+]e. Addition of AVP reversed this inhibitory effect of increased [Ca2+]e. Under hypotonic perfusion conditions (lumen 50 mmol/l NaCl; bath 150 mmol/l NaCl), a high [Ca2+]e induced a 50% decrease in Mg2+ reabsorption which was restored by AVP. Under these conditions, the effects on Ca2+ transport described above were still observed. In conclusion, activation of the CaR in the mouse TAL has no effect on basal and AVP-stimulated transepithelial NaCl reabsorption despite its large inhibitory effect on cAMP synthesis. The CaR, however, could play a role in the regulation of transepithelial Ca2+ and Mg2+ reabsorption.     

The renal medullary thick ascending limb as a model for understanding lipid mediators in sepsis

OBJECTIVE: To evaluate the impact of HIV illness on psychiatric and psychosocial functioning over 3 years in a sample of male and female HIV-positive injecting drug users (IDU), with a comparison group of HIV-negative male and female IDU. DESIGN: As part of a multidisciplinary study, 121 men (69 HIV-positive, 52 HIV-negative) and 66 women (36 HIV-positive, 30 HIV-negative) were evaluated semiannually for seven visits. Attrition, unrelated to sex or serostatus, was 33%. RESULTS: At baseline, rates of major depression and dysthymia ranged from 15% (HIV-negative men) to 33% (HIV-positive men and HIV-negative women). Global impairment was in the range found in psychiatric patients (mean Global Assessment of Functioning scores, 46-51). Higher levels of social support and less social conflict were independently associated with decreased distress and improved global functioning among both men and women. For both HIV-positive groups, degree of improvement over time was related to degree to HIV progression: those who remained healthier in terms of CD4 count and illness stage showed more improvement. HIV-seronegative status was associated with less distress for men but not for women. Overall, women reported higher levels of psychiatric distress than men. CONCLUSIONS: High rates of psychopathology were found in this IDU cohort, independent of HIV status and sex. Although rates of psychopathology, injecting drug use and distress declined slightly during the study, they remained elevated; accordingly, psychiatric services are indicated for this population.     

A Ba(2+)-insensitive K+ conductance in the basolateral membrane of rabbit cortical thick ascending limb cells

The nature of the K+ exit across the basolateral membrane of microperfused rabbit cortical thick ascending limbs (cTALs) was investigated using the transepithelial and transmembrane potential difference (PDte, PDbl) and conductance measurements. An increase in bath K+ concentration from 4 to 10, 25, 50 mmol/l depolarized the basolateral membrane in a concentration-dependent manner, accompanied by a decrease in the fractional resistance of the basolateral membrane (FRbl). The Cl- channel blocker, 5-nitro-2-(3-phenylpropyl-amino)-benzoic acid (NPPB), did not prevent these effects. The effect of Ba2+ on PDbl was bimodally distributed: paradoxically, in the tubules in which Ba2+ largely depolarized, the effects on PDbl of the bath K+ concentration increases were not inhibited by extracellular Ba2+, in tubules in which Ba2+ moderately depolarized, Ba2+ partially inhibited the K+ concentration increase-induced depolarization of the basolateral membrane. However, the parallel decrease in FRbl was Ba2+ insensitive, indicating that the K+ channel of the basolateral membrane was not modified by extracellular Ba2+. The Ba(2+)-induced depolarizations were prevented by furosemide suggesting that Ba2+ acts by inhibiting basolateral KCl extrusion. Finally, the K+ concentration increase-induced depolarizations were insensitive to tetraethylammonium, charybdotoxin, apamin and verapamil. In conclusion, the present study provides evidence that, in addition to a Ba(2+)-sensitive KCl cotransport system, the basolateral membrane of rabbit cTAL cells possesses a K+ conductance which is insensitive to extracellular Ba2+.     

Endogenous dopamine regulates phosphate reabsorption but not NaK-ATPase in spontaneously hypertensive rat kidneys

Dopamine's modulatory actions on signal transduction in the spontaneously hypertensive rat (SHR) proximal tubule are blunted; therefore, it was predicted that dopamine does not regulate phosphate (Pi) reabsorption in SHR. To test this hypothesis, dopamine production was inhibited with carbidopa (10 mg/kg ip) 18 h before and during clearance measurements of chronically denervated SHR and Wistar-Kyoto (WKY) rat kidneys. Dopamine excretion decreased 80% from SHR and 85% from WKY rats. Pi excretion decreased 60 to 67%. Plasma Pi and calcium, inulin clearance, and Na excretion did not change. Citrate excretion, which reflects proton secretion by proximal tubules, decreased 72% from WKY rats. Citrate excretion was significantly lower from SHR (5 +/- 10 pmol/min) than from WKY rats (73 +/- 11 pmol/min) and was not altered by carbidopa. Carbidopa, injected 18 and 1 h before kidneys were collected, increased NaK-ATPase in cortical basolateral membranes from WKY rats (27%) but not in membranes from SHR. After the incubation of renal cortical minceates for 15 min with L-DOPA (10(-5) M), there was no change in brush border membrane vesicle uptake of 32Pi, (3H)glucose, or (14C)citrate. Incubation with carbidopa (10(-4) M) increased 32Pi uptake by 11% (P < 0.001) and (3H)glucose uptake by 9% (P = 0.02). (14C)citrate uptake was not increased by carbidopa but was higher in SHR (977 +/- 2 pmol/10 s.mg) than in WKY rats (823 +/- 43 pmol/10 s.mg; P = 0.04). In summary, dopamine produced in WKY rat and SHR proximal tubules decreases Pi uptake by using a signaling process distinct from those that regulate NaK-ATPase and the antiporter.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protective effect of prostaglandin E2 on cerulein-induced rat pancreatitis]

In order to clarify the effect of prostaglandin E2 (PGE2) on cerulein-induced rat pancreatitis, we investigated the interaction of PGE2 with cerulein or secretin. Intravenous infusion of 10 micrograms/kg.h cerulein inhibited external secretion of the pancreas from one hour and caused macroscopic edema at 3 hours. Administration of PGE2 relieved the inhibitory effect of supramaximal dose of cerulein and decreased the pancreatic edema. The 100 micrograms/kg.hr PGE2 had no significant effect on the pancreatic juice volume and amylase secretion stimulated with 0.2 micrograms/kg.hr of cerulein. Intravenous injection of 100 micrograms/kg PGE2 inhibited both the volume and amylase secretion of pancreatic juice stimulated with 1 U/kg.h of secretin. The protective effect of PGE2 on cerulein-induced pancreatitis was not the stimulation on secretion but caused the cytoprotective effect of PG such as stabilization of cytoplasmic and lysosomal membrane.     

Inhibition of voltage-dependent calcium channels by prostaglandin E2 in rat melanotrophs

The effects of PGE2 on voltage-dependent Ca2+ channel currents were studied in dissociated rat melanotrophs by the whole-cell configuration of the patch-clamp technique. In about 90% of melanotrophs examined, PGE2 reversibly inhibited voltage-dependent Ba2+ currents elicited by voltage steps from a holding potential of -80 to 0 mV, with an ED50 of 68 nM. The maximum inhibition of Ba2+ currents by 1 microM PGE2 (35.3%) was comparable with that by the maximally effective concentration (100 nM) of dopamine. The EP1/EP3 PGE (EP) agonists, 17PT-PGE2 and sulprostone, and the EP2/EP3 agonist, misoprostol, mimicked the inhibition by PGE2, whereas the selective EP2 agonist, butaprostol, had little effect. The inhibition by PGE2 was partially, but significantly, reduced by the selective EP1 antagonist, SC-51322. The magnitude of the PGE2-induced inhibition of Ba2+ currents was greatly reduced by pretreatment with pertussis toxin, or by a depolarizing prepulse, to +80 mV, lasting for 50 msec. Although four distinct types (N-, P/Q-, L-, and R-types) of high-threshold Ba2+ currents were observed, PGE2 (1 microM) caused significant inhibition of only P/Q- and L-type currents, which were 17.3 and 10.1%, respectively, of the total Ba2+ currents. These results suggest that PGE2 inhibits P/Q- and L-type Ca2+ channels of rat melanotrophs via EP1 and EP3 receptors, which are coupled to pertussis toxin-sensitive G proteins, and produces both voltage-sensitive and -insensitive inhibition of Ca2+ channels.     

Effects of salt depletion on the kidney: changes in medullary oxygenation and thick ascending limb size

Previous studies have shown that salt depletion enhances the susceptibility of the kidney to nephrotoxins (amphotericin, cyclosporine, and contrast). To study the renal response to salt depletion, Sprague-Dawley rats were fed a sodium-deficient diet (N = 12) with pair-fed controls (N = 13) for 4 wk. In addition, rats from each group underwent 24-h water deprivation studies (N = 9; four salt deprived, five normal). Plastic 1-micron horizontal sections of mid-inner stripe were examined, and cross-sectional areas of the medullary thick ascending limb (mTAL) were analyzed. The mTAL of the salt-deprived rats were smaller (P = 0.04) and showed greater variance in size (P = 0.02) than control (618 +/- 106 versus 693 +/- 50 microns2). However, mean glomerular and collecting duct cross-sectional areas were unaffected by salt intake. Cross-sectional areas of long- and short-loop mTAL were significantly different, regardless of group (518 +/- 78 versus 732 +/- 92 microns2). Maximal urinary concentrating ability was found to correlate with mTAL cross-sectional area (r = 0.85; P = 0.004) and with long-loop mTAL size (r = 0.77; P = 0.016). However, it did not significantly correlate with short loop mTAL size (r = 0.53; P = 0.14).(ABSTRACT TRUNCATED AT 250 WORDS)     

Prenatal in vivo bulbourethral gland development is not affected by prostaglandin E2 inhibition

Investigation of bulbourethral gland (BUG) development is useful to study genitourinary (GU) tract growth and differentiation. Understanding GU tract growth and differentiation is relevant to testing the hypothesis that the initial lesion of human benign prostatic hyperplasia involves focal re-expression of inductive processes in the periurethral region of the prostatic transitional zone. Prostaglandins play a role in regulating growth and morphogenesis of different organ systems. Previous reports have proposed that prostaglandin E2 (PgE2) mediates the masculinizing effects of testosterone in the developing neonatal male GU tract. We have previously shown that androgens lower rather than raise BUG PgE2 levels. Further studies led us to conclude that PgE2 does not play a major role in postnatal BUG growth and morphogenesis in vitro. In order to investigate the possible role of PgE2 in prenatal BUG development, indomethacin (INDO, 1.0 mg/kg- day, subcutaneously) was administered to pregnant BALB/c mice on gestational days 12-18. Control pregnant mice were either untreated or injected with dimethylsulfoxide vehicle. Anogenital distances were measured within 12 hours after birth in male and female offspring on day 19. In male neonatal mice, BUGs were examined histologically and PgE2 levels were measured by radioimmunoassay in BUGs and whole genital tracts. We observed no significant morphological differences in INDO-exposed BUGs compared to controls. No significant differences in mean anogenital distances of INDO-exposed male offspring or controls were detected. Mean anogenital distances of female offspring were similar in the three respective groups. Mean BUG PgE2 levels in INDO-exposed neonates were significantly lower (P < 0.05) than in untreated neonates.(ABSTRACT TRUNCATED AT 250 WORDS)     

In vivo formation of prostaglandin E1 and prostaglandin E2 in atopic dermatitis

The authors present the young man case who had undergone 6 months long antibiotic therapy first, than has been operated because of growing nose obstruction with bloody pus secretion. Diagnostic difficulties were responsible for diagnosis and undertaking treatment. Fulminant course of disease resulted in death of patient in the course of immunosupression therapy.     

Concentrating defect in experimental nephrotic syndrone: altered expression of aquaporins and thick ascending limb Na+ transporters

BACKGROUND: Several pathophysiological states associated with deranged water balance are associated with altered expression and/or intracellular distribution of aquaporin water channels. The possible role of dysregulation of thick ascending limb NaCl transporters, which are responsible for countercurrent multiplication in the kidney, has not been evaluated. METHODS: Semiquantitative immunoblotting and immunocytochemistry were carried out in the kidneys of rat with adriamycin-induced nephrotic syndrome and in vehicle-injected control rats. RESULTS: Preliminary studies confirmed the presence of a severe concentrating defect. Semiquantitative immunoblotting of outer medullary homogenates demonstrated a marked decrease in the abundance of three thick ascending limb Na+ transporters in nephrotic rats, namely the bumetanide-sensitive Na-K-2Cl cotransporter (BSC-1), the type 3 Na/H exchanger (NHE-3), and the alpha 1-subunit of the Na-K-ATPase. These results are predictive of a decrease in the NaCl transport capacity of the medullary thick ascending limb and therefore a decrease in countercurrent multiplication. Immunocytochemistry of outer medullary thin sections demonstrated broad (but highly variable) suppression of BSC-1 expression in the outer medullas of adriamycin-nephrotic rats. There was also a large decrease in outer medullary expression of two collecting duct water channels (aquaporin-2 and -3) and the major water channel of the thin descending limb of Henle's loop (aquaporin-1). CONCLUSION: The concentrating defect in adriamycin-induced nephrotic syndrome in rats is a consequence of multiple defects in water and solute transporter expression, which would alter both the generation of medullary interstitial hypertonicity and osmotic equilibration in the collecting duct. Whether a similar widespread defect in transporter expression is present in idiopathic nephrotic syndrome is, at this point, untested.     

Repair of rat gastric mucosa: effect of 16,16-dimethyl prostaglandin E2

Coadministration with the human immunodeficiency virus (HIV) protease inhibitor ritonavir was investigated as a method for enhancing the levels of other peptidomimetic HIV protease inhibitors in plasma. In rat and human liver microsomes, ritonavir potently inhibited the cytochrome P450 (CYP)-mediated metabolism of saquinavir, indinavir, nelfinavir, and VX-478. The structural features of ritonavir responsible for CYP binding and inhibition were examined. Coadministration of other protease inhibitors with ritonavir in rats and dogs produced elevated and sustained plasma drug levels 8 to 12 h after a single dose. Drug exposure in rats was elevated by 8- to 46-fold. A > 50-fold enhancement of the concentrations of saquinavir in plasma was observed in humans following a single codose of ritonavir (600 mg) and saquinavir (200 mg). These results indicate that ritonavir can favorably alter the pharmacokinetic profiles of other protease inhibitors. Combination regimens of ritonavir and other protease inhibitors may thus play a role in the treatment of HIV infection. Because of potentially substantial drug level increases, however, such combinations require further investigation to establish safe regimens for clinical use.     

Distribution of prostaglandin E receptors in the rat gastrointestinal tract

AIMS: In order to study the role of prostaglandin in the regulation of the gastrointestinal functions, gene expression of prostaglandin receptors along the rat gastrointestinal tracts were investigated. METHODS: Rats were used for the study. The combination of counterflow elutriation separation of mucosal cells and Northern blot analysis was used to detect the gene expression of prostaglandin receptors in gastrointestinal tracts. RESULTS: In small intestine and colon, prostaglandin E2 EP1 and EP3 receptor mRNAs were mainly localized in the deeper intestinal wall containing muscle layers. EP4 receptor gene expression, on the other hand, was detected in the intestinal mucosal layer. In the stomach, EP1 mRNA was detected in gastric muscle layers, whereas EP3 and EP4 receptor gene expression was mainly present in the gastric mucosal layer containing epithelial cells. In gastric epithelial cells, parietal cells were found to have both EP3 and EP4 receptors. At lower concentrations, prostaglandin E2 inhibited gastric acid secretion by parietal cells probably through EP4 receptors. At higher concentrations, however, it stimulated it. On the other hand, mucous cells possessed only EP4 receptor mRNA. CONCLUSIONS: Thus, it is suggested that prostaglandin E2 modulates gastrointestinal functions through at least three different prostaglandin receptors (EP1, EP3, and EP4), each of which has a distinct contribution in the gastrointestinal tract.     

Localization of cyclooxygenase-2 and prostaglandin E2 receptor EP3 in the rat lumbar spinal cord

Cyclooxygenase-2 (COX-2) is now considered to be the major constitutively expressed COX isozyme in the central nervous system. The present immunocytochemical study details localization of COX-2 immunoreactivity in rat spinal cord along with the expression of prostaglandin E2 receptor subtype EP3. Prominent COX-2 staining was observed in the nuclear envelope of neurons throughout the spinal cord, especially in the superficial dorsal horn laminae and motoneurons of lamina IX, as well as in glial cells of the white matter. Expression of EP3 receptor was strictly confined to afferent terminal areas in the superficial dorsal horns.