Antidiuretic hormone reduces the high PGE2 synthesis in papillary collecting duct of DI rats

PGE₂ synthesis was measured along the nephron of Brattleboro (DI) rats, lacking ADH, and control LE rats, using an enzyme immunossay. Experiments were performed in vitro, in the absence of exogenous arachidonic acid, using microdissected tubular segments. The effect of a chronic treatment by dDAVP was tested on three ADH sensitive tubular segments, medullary thick ascending limb (MTAL), medullary collecting tubule (OMCD) and papillary collecting duct (IMCD).No difference in PGE₂ synthesis was present between LE and DI in glomerulus and tubular segments up to OMCD. In both strains, values were low in the proximal tubule and the loop of Henle, and gradually increased along the collecting tubule. In IMCD, PGE₂ synthesis was much higher in DI (12.8±2.0 pg per 30 min per mm tubular length) than in LE (3.8±0.5, LE vs. DIp<0.001).In MTAL and OMCD, dDAVP treatment did not affect PGE₂ synthesis. In IMCD, dDAVP reduced PGE₂ synthesis to values (5.3±0.8 pg per 30 min per mm tubular length), which were not significantly different from those of LE. Neither oxytocin, which has been shown to be elevated in DI rats, nor furosemide, that reduced papillary osmolarity to values comparable to those of DI rats, were able to increase PGE₂ synthesis in IMCD of LE rats. The mechanism of the increase in PGE₂ synthesis in IMCD of DI rats, and of the inhibitory effect of dDAVP is yet unknown; it may participate to compensate for the lack of ADH in the Brattleboro rat.     

Intrathecal administration of prostaglandin E2 causes sensitization of the primary afferent neuron via the spinal release of glutamate

Objective and Design: The present investigation was aimed at assessing the involvement of primary sensory neurons in the hyperalgesia induced by the intrathecal injection of PGE₂, as well as whether the hyperalgesic effect was due to the spinal release of glutamate. Material: Male Wistar rats were used. Methods: Hyperalgesia was measured using the rat paw pressure test. Results: Intrathecal PGE₂ (2.5–50 ng/rat) administration caused a dose-dependent hyperalgesia in both paws. Ipsilateral intraplantar injections of morphine (0.5–8 μg/paw) or SNAP (S-nitroso-N-acetyl-D,L-penicillamine, 50–200) μg/paw) dose-dependently antagonized spinally-induced PGE₂ hyperalgesia (ANOVA, p<0.001). Their antinociceptive effects were confirmed to be peripheral by abolition following pretreatment of the paws with L-NMMA (N^G-monomethyl-L-arginine monoacetate), 50 μg/paw or with methylene blue (500 μg/paw). The spinally-induced PGE₂ hyperalgesia was antagonized by intrathecal injections (9 μg) of AP5 (2-amino-5-phosphonopentanoate/2-amino-5) a selective NMDA receptor antagonist. Conclusions: Intrathecal administration of PGE₂ seems to cause hyperalgesia by spinal sensitization of the primary afferent neuron through the release of glutamate. accepted by K. Brune and M. J. Parnham     

Effect of intravenous prostaglandin E1 on thrombolysis induced by human recombinant tissue-type plasminogen activator in feline peripheral arterial thrombosis

We have assessed the efficacy of prostaglandin E₁ (PGE₁) iv infusions in accelerating the rate of reperfusion achieved with human recombinant tissue-type plasminogen activator (r-t-PA or t-PA) in feline arterial thrombosis. Occlusive clots were formed in the femoral arteries of adult male cats by placing a copper coil within the vessel. Thrombolytic therapy was started 90 to 150 min later if angiograms confirmed vessel occlusion. All cats received t-PA at an iv dose of 1 mg/kg (over 2 h) in combination with either PGEI or its vehicle. Mean aortic blood pressure (MAP) was continuously monitored and arteriograms were performed at 15 min intervals to assess time to femoral artery reflow. PGE₁ doses ranged from 0.1 to 30 μg/kg/min; infusions ≥ 0.3 μg/kg/min were associated with significant reductions (p<0.01) in ex vivo platelet reactivity to adenosine 5′-diphosphate (ADP). Reflow times achieved with t-PA (65±7min, n=9) were significantly reduced by co-infusion of 0.3μg/kg/min PGE₁ (30±5 min, n=7, p<0.01). PGE₁'s effect was compromised at both lower (0.1 μg/kg/min) and higher (3.0 and 30 μg/kg/min) doses. The higher doses of PGE₁ were accompanied by marked hypotension (MAP decrease > 30%). These results show that in feline peripheral arterial thrombosis iv PGE₁ can improve the thrombolytic effect of t-PA. This enhancing effect of PGE₁ can best be achieved at threshold platelet inhibitory doses having minimal haemodynamic effects. This latter factor would limit the utility of intravenous PGE₁ for this indication because of its potent vasodilatory properties.     

Haemodynamic conditions for renal PGE2 and renin release during α- and β-adrenergic stimulation in dogs

Constriction of the renal artery and infusion of an α-adrenergic agonist induce autoregulated vasodilation and increase prostaglandin E₂ (PGE₂) and renin release. The enhancement of renin release during autoregulated vasodilation might be mediated by prostaglandins. To examine this hypothesis, experiments were performed in three groups of anaesthetized dogs. In six dogs constriction of the renal artery to a perfusion pressure below the range of autoregulation raised renin release from 2 ± 1 to 27 ± 6 μg AI.min^-1 and PGE₂ release from 1 ± 1 to 10 ± 2 pmol. min^-1. After administration of indomethacin (10 mg. kg^-1 b. wt), PGE₂ release was effectively blocked and constriction of the renal artery raised renin release only from 0.1 ± 0.1 to 6 ± 1 μg AI.min^-1. During subsequent continuous infusion of a β-adrenergic agonist, isoproterenol (0.2 μg. kg^-1.min^-1), constriction of the renal artery raised renin release from 0.1 ± 0.1 to 52 ± 11 μg AI.min^-1, although there was no rise in PGE₂ release. In six dogs, intrarenal infusion of phenylephrine, an α adrenergic agonist, increased PGE₂ and renin release before, but not after, indomethacin administration. In six other dogs, phenylephrine infused during isoproterenol infusion increased renin release equally before and after indomethacin administration. Thus the enhancing effect of constricting the renal artery or infusing an α-adrenergic agonist is not dependent upon prostaglandins. We propose that autoregulated dilation enhances renin release whether the stimulatory agent is a prostaglandin or a β-adrenergic agonist.     

Central cardiovascular and thermal effects of prostaglandin E2 in rats1

Prostaglandin E₂ (PGE₂) increased the blood pressure, heart rate and body temperature, when administered at the doses of 0.001–10 μg into the lateral cerebral ventricle (i. c. v.) of the urethane-anesthetised rat. The highest dose of 10 μg/rat induced a strong initial hypotensive effect. Intravenously (i. v.), PGE₂ at the doses of 0.01–10 μg/rat caused a biphasic blood pressure response with dose-related initial decreases followed by slight increases in blood pressure. The heart rate and body temperature were slightly increased by i. v. administrations of PGE₂. The highest i. v. dose of 10 μg/rat initially decreased also the heart rate. Central pretreatment with indomethacin (1 mg/rat i. c. v.) partly antagonised all of the recorded central effects of PGE₂, while sodium meclofenamate (1 mg/rat i. c. v.) abolished the hypertensive response to i. c. v. administered PGE₂ but failed to significantly affect the PGE₂-induced rises of heart rate and body temperature. The results support the previous suggestions that PGE₂ may participate in the central cardiovascular and thermoregulatory control. The results also suggest that indomethacin and sodium meclofenamate antagonize the effects of exogenous prostaglandins. Since sodium meclofenamate, unlike indomethacin, affected preferentially the hypertensive response to centrally administered PGE₂, there may be differences in the sites and/or modes of action between these drugs.     

Sulphasalazine and experimental stress ulcers

The effects of sulphasalazine on gastric ulceration induced by restraint at 4°C (stress) for 2 h were studied in rats. Doses of 63 or 125 mg/kg s.c., which had no effect on stomach wall prostaglandin E₂ (PGE₂) levels, prevented stress ulceration but not the lesions produced by indomethacin. Stress significantly increased gastric glandular mucosal PGE₂ levels. Indomethacin pretreatment (20 mg/kg, p.o.) markedly reduced PGE₂ levels in the same region of the stomachs, and worsened stress-induced lesion formation. Pretreatment with sulphasalazine of animals given indomethacin and then subjected to stress did not appear to affect the indomethacin component of indomethacin-stress ulceration. Oral administration of PGE₂ 200 g/kg significantly elevated gastric PGE₂ levels, but had no effect on stress ulceration.It appears that neither the antiulcer activity of sulphasalazine nor stress-induced ulceration is associated with gastric tissue PGE₂ increase or decrease, respectively. The protective mechanism may result from the ability of sulphasalazine to inhibit lipoxygenase activity.     

Effect of the COX-2 Selective Inhibitor L-745,337 on Inflammation and Organ Prostaglandin E2 (PGE2) Levels in Adjuvant Arthritic Rats

The anti-inflammatory activity of the cyclooxygenase-2 inhibitor, L745,337, was assessed in adjuvant arthritic rats (AA). The relationship between PGE₂ organ levels and drug activity or adverse effects was determined. Arthritic rats were orally treated for two weeks with L-745,337 (0.1, 1 and 5 mg/kg/day), indomethacin (1 mg/kg/day) or vehicle and paw swelling was determined. At the end of the study, samples from paw, stomach (wall and mucosa) and kidney were obtained from rats with or without treatment at high doses of L-745,337 or indomethacin and PGE₂ levels were determined. The L-745,337 anti-inflammatory effective-dose-50 was 0.4 mg/kg. Maximal anti-inflammation was obtained with L-745,337 or indomethacin at doses of 5 and 1 mg/kg respectively. L-745,337 showed anti-arthritic activity. No stomach ulcers appeared in either untreated or treated arthritic and healthy control rats. In AA rats, PGE₂ increased in paw, stomach wall, gastric mucosa and kidney. These levels were lower in all organs after both drugs but not below PGE₂ control levels.     

Inhibition of lymphocyte response by prostaglandin-producing suppressor cells in patients with melanoma

Peripheral blood mononuclear cells (PBMC) from 11 patients with metastatic melanoma (group II) had a significant decrease in blastogenesis to concanavalin A (Con A) (38.7±7.7 cpm × 10³; mean ± SE) compared to 21 patients who were disease free (70.6±6.7) or 16 healthy controls (83.6±10.3). If PBMC from patients were preincubated for 72 hr prior to exposure to mitogen, blastogenesis was restored to normal. In group II patients a similar improvement in reactivity of fresh PBMC occurred with indomethacin addition or following rigorous depletion of adherent monocytes. Supernatants from cells cultured with and without Con A in several group II patients contained very high levels of endogenous PGE₂. Patients had a greater percentage of T lymphocytes bearing Fc receptors for ox erythrocytes (T_γ) than controls, which appeared to correlate with the increased sensitivity to suppression by exogenously added PGE₂. These data suggest that the decreased blastogenesis in certain melanoma patients is due to an increase in PGE₂ production by monocytes, along with an increase in lymphocyte sensitivity to its effects.     

Influence of prostaglandin E2 and indomethacin on interferon-γ production by cultured peripheral blood leukocytes of multiple sclerosis patients and healthy donors

The addition of indomethacin to concanavalin A (Con A)-induced cultures of human peripheral blood leukocytes (PBL) caused an increase in interferon response, regardless of whether the PBLs were derived from multiple sclerosis (MS) patients or from control donors. Specifically the response rates increased from 71 to 100% in controls and from 24 to 53% in MS patient-derived cultures. The amounts of interferon produced also increased in both groups by 0.8 log U/ml. However, interferon yields of nonresponsive cultures becoming interferon-producing only after indomethacin treatment remained relatively low. In control cultures, maximal increases of interferon production were obtained with doses of 0.05 to 0.1 µg/ml indomethacin; for MS patients higher doses were needed—0.1 to 0.5 µg/ml. Conversely, a relatively low dose (0.05 µg/ml) of exogenous prostaglandin E₂ (PGE₂) was able to inhibit interferon production completely in MS patient-derived cultures, whereas in control cultures higher doses were needed (0.1 to 1.0 µg/ml). Analysis of endogenous PGE₂ levels in the PBL cultures revealed that PGE₂ production was similar in nonresponder MS cultures and responder control cultures but that MS leukocytes were more sensitive to the inhibitory effect of PGE₂ on interferon production. We conclude that in a minor percentage of MS patient-derived PBL cultures, the deficiency in interferon- (IFN-) production can be (partially) overcome by treatment of the cells with indomethacin. However, in the major part of nonresponder MS cultures, indomethacin has no effect, indicating that the PG system is not the major cause for the defective interferon response in MS.     

Increased activity of the Na-K-ATPase in red cell-ghosts of patients with Cushing's Syndrome: Possible significance for the pathogenesis of glucocorticoid-induced hypertension

Summary The Na-K-ATPase activity of erythrocyte ghosts was increased in 6 patients with Cushing's syndrome compared with 28 control subjects (0.986±0.291 versus 0.259±0.1 µM P_i·h^–1·mg^–1,p<0.001). Ouabain insensitive Mg-ATPase activity was similar in both groups. These data support the concept of an activation of the Na-pump in patients with glucocorticoid excess.     

Renal Na-K-ATPase Activity during Saline Infusion in the Rabbit

During saline infusion, sodium reabsorption (R_Na) in the diluting segment (thick ascending limb of Henle's loop) increases acutely. The mechanism for this higher pumping rate of outer medullary Na-K-ATPase is unknown. Following left-sided nephrectomy, immediate i.v. infusion of hypertonic saline increased R_Na in the remaining whole right kidney by 28 ± 14% (p < 0.05). Na-K-ATPase activity in outer medulla was raised by (A) 23 + 4% above the left kidney (p < 0.05), whereas cortical activity was unchanged. The mechanism for this increase in Na-K-ATPase activity was explored. The catalytic rate per enzyme did not differ in the two kidneys and equalled 5 340 min^-1. The increase was therefore due to higher tissue concentration of active enzyme. The response was fully developed during continuous infusion within 20 min, and of equal magnitude whether protein synthesis had been inhibited by cycloheximide (Δ= 23 ± 7%) or stimulated by unilateral nephrectomy 6 days earlier combined with saline infusion for 2 h (Δ= 34+ 10 %). Thus, during hypertonic saline infusion, the increased R_Na in the outer medulla was partly accounted for by the activation of latent Na-K-ATPase. High delivery of sodium to the diluting segment for more than 20 min during hypertrophy caused no further activity change.     

Regulation of extravascular fibrinolysis by factor XIII

The stability of fibrin clots in the extravascular compartment was examined using samples of ¹²⁵I-labelled fibrin implanted subcutaneously into Balb/c mice. These samples of ¹²⁵I-labelled fibrin were prepared in vitro. Crosslinking of fibrin in the presence of a high level of factor XIIIa resulted in complete conversion of γ-chain monomers to γ-γ dimers and extensive covalent polymerisation of the α-chain monomers. This fibrin, categorised as fully crosslinked (FXL), showed a 50% clot lysis time (LT-50) of 9.6±0.8 days. In contrast, fibrin, termed as partially crosslinked (PXL), prepared with a low level of Factor XIIIa, had all of its γ-chain monomers converted γ-γ dimers, but only a portion of its α-chain monomer polymerised. This PXL fibrin showed an LT-50 of 4.8±1.1 days. Non-crosslinked (NXL) fibrin displayed an LT-50 of 5.2±1.2 days. Fibrin produced by the addition of thrombin to plasma was of the PXL type and gave an LT-50 of 4.2±1.0 days. Fibrin produced by the addition of thrombin to whole blood, on the other hand, was found to be FXL and showed an LT-50 of 13.0 ± 2.0 days. Western blot analysis of fibrin samples prepared from plasma and whole blood with the use of antibody to α₂-plasmin inhibitor (α₂-PI) provided evidence that this inhibitor was covalently crosslinked to fibrin from both sources. FXL fibrin proved far more stable than either PXL fibrin or NXL fibrin to fibrinolysis by leukocyte elastase in vitro (p<0.001). Inclusion of the specific elastase inhibitor Elastatinal in the implanted NXL fibrin clot extended the LT-50 from 5 to 11.7 days (p<0.001), whereas a plasmin inhibitor, ϵ-amino caproic acid caused no change in lysis time. These results suggest that extravascular fibrinolysis is mediated chiefly by leukocyte proteases and that factor XIIIa-catalysed α-chain crosslinking is essential for protection of extravascular clots against fibrinolysis by these proteases.     

Minocycline reduces prostaglandin E synthase expression and 8-isoprostane formation in LPS-activated primary rat microglia

Minocycline is a tetracyclic antibiotic whose non-antibacterial activities, including anti-inflammatory, antinociceptive, and neuroprotective effects, have been widely studied. Thus, a better understanding of the mechanisms underlying its pleiotropic activities is important. Primary microglial cell cultures were established from cerebral cortices of 1-day neonatal Wistar rats. Minocycline (3–100 µM) or its vehicle was added to the culture media 30?min prior to 24?h incubation with lipopolysaccharide (LPS; 10?ng/mL). Cell viability after these treatments was assessed by ATP-based luminescence test. Prostaglandin (PG) E₂ and 8-iso-PGF_2α were determined by enzyme immunoassays. Cyclooxygenase-2 and microsomal PGE₂ synthase-1 protein levels were measured by western blot analysis. First, it was shown that minocycline (30 or 100 µM) inhibits PGE₂ production in LPS-activated primary rat microglial cells. Then, by investigating targets involved in this inhibition, it was found that minocycline (3–100 µM) inhibits microsomal PGE₂ synthase-1, but not cyclooxygenase-2, expression. Additionally, minocycline (3–100 µM) inhibited the production of 8-iso-PGF_2α. This study warrants the conduction of in vivo studies to evaluate the pharmacological relevance of these findings.     

Protection of the rat gastric mucosa by prostaglandin E2: Possible relation to stimulation of the alkaline secretion

Exogenous prostaglandins have specific protective effects on the gastric mucosa called cytoprotection which is proposed to be connected to the stimulatory effects of prostaglandins on the gastric nonparietal secretions. The protection by oral prostaglandin E₂ (PGE₂) against indomethacin-induced gastric erosions was studied in the rat, as was the effect on the protection of blocking the gastric alkaline secretion by acetazolamide. PGE₂ reduced dose-dependently the indomethacin gastric erosion formation, confirming previous results from others. Acetazolamide caused very little damage when given alone but potentiated the indomethacin erosion formation in a dose-related way. PGE₂ was less protective or without effect against lesions caused by indomethacin when given together with acetazolamide, but protection could be obtained by increasing the doses of PGE₂. Indomethacin and acetazolamide are both blockers of the gastric bicarbonate secretion, which is stimulated by PGE₂. The potentiation of indomethacin induced lesions by acetazolamide and the antagonistic actions between acetazolamide and PGE₂ on mucosal protection are compatible with the hypothesis that stimulation of the alkaline secretion is one mechanism of cytoprotection of the gastric mucosa by PGE₂.     

Comparisons of clinical features and outcomes between Elizabethkingia meningoseptica and other glucose non-fermenting Gram-negative bacilli bacteremia in adult ICU patients

BackgroundClinical information of Elizabethkingia meningoseptica (EM) bacteremia in intensive care unit (ICU) patients is limited and the impact on outcomes uncertain. The aim of this study was to investigate the clinical features and impact of EM bacteremia compared to other glucose non-fermenting Gram-negative bacilli (GNF-GNB) bacteremia in ICU patients.MethodsThis retrospective cohort study enrolled 70 patients who developed GNF-GNB bacteremia after ICU admission, including 19 cases of EM bacteremia (19/70, 27.1%). The main outcome measure was in-hospital mortality.ResultsThe patients with EM bacteremia had a lower rate of appropriate antibiotic therapy (15.8% vs. 62.7%, p < 0.001) and a longer time to appropriate antibiotic therapy (76.8 ± 46.4 vs. 35.1 ± 38.7 h, p < 0.001), but with a less severity in acute physiology and chronic health evaluation (APACHE) II score and shock status (p < 0.05) at the onset of bacteremia, compared to those with non-EM bacteremia. The in-hospital mortality between those with EM bacteremia and non-EM bacteremia was similar (63.2% vs. 51.0%, p = 0.363). However, primary bacteremia was more frequently noted in EM compared with non-EM group (57.9% vs. 25.5%, p = 0.011), and odds ratio 4.294 (95% confidence interval 1.292–14.277, p = 0.017) in multivariate regression analysis.ConclusionAmong the patients with GNF-GNB bacteremia, the numbers of the cases with primary bacteremia and inappropriate therapy were significantly more in EM group than those in non-EM group.     

Acute resistance exercise reduces blood pressure and vascular reactivity, and increases endothelium-dependent relaxation in spontaneously hypertensive rats

The aim of the present study was to assess the effects of acute dynamic resistance exercise on resting blood pressure (BP) and on endothelial function of vascular bed of spontaneously hypertensive rats. Hemodynamic measurements were performed before and after acute dynamic resistance exercise in conscious animals. After exercise, the tail artery was cannulated for mean perfusion pressure with constant flow measurement and for performing concentration–response curves to acetylcholine (ACh) and sodium nitroprusside (SNP) and dose–response curves to phenylephrine (PHE). PHE protocol was also repeated with damaged endothelium and after L-NAME and indomethacin perfusion on the tail. The maximal response (E _max) and sensitivity (pD₂) were evaluated to these drugs. Exercise reduced resting systolic and diastolic BP (Δ −79 ± 1.8; −23 ± 2.3 mmHg, respectively; P < 0.05). ACh-induced relaxation increased in the exercise group (pD₂ = 9.8 ± 0.06, P < 0.05) when compared with control rats (pD₂ = 8.7 ± 0.1). The E _max to PHE with intact endothelium decreased following exercise condition (439 ± 18 mmHg, P < 0.05) when compared with control rats (276 ± 22 mmHg). This response was abolished after L-NAME and indomethacin administration. After damage of the endothelium, PHE responses were not significantly different between the groups; however, E _max and pD₂ increased when compared with responses obtained with intact endothelium. The results demonstrated that acute dynamic resistance exercise decreased resting BP and reactivity to PHE and increased endothelium-dependent relaxation. Nitric oxide and vasodilators prostanoids appear to be involved in post-exercise endothelial and pressor responses.     

Evidence for interference of vitamin D with PTH/PTHrP receptor expression in opossum kidney cells

 Vitamin D counters the phosphaturic action of parathyroid hormone (PTH) in rats in vivo. The present study was undertaken to examine this interaction using monolayers of Opossum kidney (OK) cells. ³²P uptake, cAMP generation, PTH/PTHrP receptor mRNA expression and intracellular Ca²⁺ [Ca²⁺]_i were measured in (1) control cells, (2) cells exposed to PTH, (3) cells pretreated with 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], and (4) 1,25(OH)₂D₃-pretreated cells exposed to PTH. ³²P uptakes were in (1) 5.00±0.20 (mean ±SE), in (2) 2.30±0.14 (P<0.001 versus group 1), in (3) 4.80±0.24 (P NS versus group 1) and in (4) 3.70±0.20 (P<0.001 versus group 2) nmol P_i/(mg·prot 10 mm). cAMP levels were in (1) 10±3, in (2) 210±8, in (3) 12±4, and in (4) 122±12 pmol cAMP/mg protein (P<0.001 versus group 2). PTH/PTHrP receptor mRNA expression was in relative units: (1) 100±0, (2) 99.5±6.2, (3) 68.7±2.6 (P<0.001 versus group 1), and (4) 34.8±3.3 (P<0.001 versus group 1). In groups 2 and 4 PTH induced equal transient increments in [Ca²⁺]_i. These experiments demonstrate that the effect of vitamin D on phosphate transport is associated with a commensurate diminution in PTH/PTHrP receptor gene expression and PTH-induced cAMP formation but not with Ca²⁺ transients. Vitamin D per se does not affect ³²P uptake or cAMP generation while it slightly decreased PTH/PTHrP receptor gene expression. These observations demonstrate that: (1) 1.25(OH)₂D₃ directly antagonizes the effects of PTH on ³²P uptake in OK cells, (2) this effect is mediated via inhibition of PTH-induced activation of AC/cAMP system, (3) the diminution in PTH-induced cAMP formation may stem at least in part from a decrease in the expression of PTH/PTHrP receptor mRNA. Received: 2 December 1997 / Received after revision: 19 January 1998 / Accepted: 28 January 1998     

Effect of atrial natriuretic factor on renal prostaglandin E2 release in the anaesthetized dog

Experiments were undertaken in two groups of barbiturate anaesthetized dogs to examine whether atrial natriuretic factor (ANF) exerts an effect on renal release of prostaglandin E₂ (PGE₂). In the first group, intravenous infusion of ANF (50 ng min^-1kg^-1body wt) reduced basal PGE₂ release from 4.4 ± 0.8 pmol min^-1to 1.8 ± 0.7 pmol min^-1. In the second group, intrarenal infusion of an α-adrenoceptor agonist, phenylephrine (2.5–6.75 μg min^-1), raised PGE₂ release from 2.7 ± 0.5 pmol min^-1to 7.5 ± 1.3 pmol min^-1. During continuous α₁-adrenergic stimulation, intravenous infusion of ANF (100 ng min^-1kg^-1body wt) reduced PGE₂ release to 3.5 ± 1.0 pmol min^-1. These results demonstrate that ANF reduces basal and α₁-adrenergic stimulated renal PGE₂ release.     

Serum calcitonin,calcium and thyroxine in young and old Zucker fatty rats (fa/fa)

We determined the serum levels of calcitonin (CT), calcium (Ca), and thyroxine (T₄) in lean (?/+) and fatty (fa/fa) male Zucker rats 10 weeks and 10–12 months of age. The most dramatic finding was a high level of serum CT (3.24±1.18 ng/ml) in young fatties whereas sera from young leans were all below the limit of assay detection (<0.120 ng/ml, p<0.01). Young fat rats also had elevated levels of both Ca (11.2±0.2 vs. 9.7±0.2 mg/dl, p<0.001) and T₄ (6.7±0.48 vs. 4.72±0.28 μg/dl, p<0.01). In older animals the mean serum level of CT increased further in the fatties and became readily measurable in leans (5.67±1.94 vs. 1.49±0.55, p<0.01). Thyroid C-cells, identified immunohistochemically, were abundant in both leans and fatties at this age but were substantially more numerous in the fat rats (p<0.001). Calcium levels increased somewhat in the older leans, but still remained higher in the fat rats (p<0.05). Thyroxine values were essentially the same for old animals of both genotypes (5.07±0.61 vs. 5.54±0.88). Age effects were not significant for any measure in the fat animals, but in the leans there were significant age-related increases in CT (p<0.02) and serum Ca (p<0.05).     

Re-establishment of gap junctional intercellular communication (GJIC) between human endometrial carcinomas by prostaglandin E2

Reduced intercellular communication via gap junctions is correlated with carcinogenesis. Gap junctional intercellular communication (GJIC), between normal human endometrial epithelial cells is enhanced when endometrial stromal cells were present in culture. This enhancement of GJIC between normal epithelial cells also occurs when they are cultured in medium conditioned by stromal cells. This observation indicated that a soluble compound (or compounds) produced and secreted by stromal cells mediates GJIC in epithelial cells. Previous studies have shown that endometrial stromal cells release prostaglandin E₂ (PGE₂) and prostaglandin F_2α (PGF_2α) under physiological conditions. When we evaluated the response of normal endometrial epithelial cells to various concentrations of PGE_2, we found enhanced GJIC with 1 nM PGE₂. This is a smaller increase in GJIC than that induced by medium conditioned by stromal cells. When the extracellular concentration of PGE₂ was measured after incubation with stromal cells, it was found to be similar to the concentrations showing maximal GJIC between the normal epithelial cells. When indomethacin was used to inhibit prostaglandin synthesis by stromal cells, GJIC was reduced but not eliminated between normal endometrial epithelial cells. These observations suggest that although PGE₂ secreted by stromal cells is an important mediator of GJIC between the epithelial cells, it is not the sole mediator. Transformed endometrial epithelial cells did not demonstrate GJIC even in the presence of stromal cells. However, we were able to re-establish GJIC in transformed epithelial cells when we added PGE₂ to the cells. Our findings show that PGE₂ may serve as an intercellular mediator between stromal and epithelial cells that regulates GJIC in normal and malignant epithelial cells. This suggests that maintenance of GJIC by preserving or replacing PGE₂ secretion by endometrial stromal cells may have the potential to suppress carcinogenesis in endometrial epithelial cells.