Renal Prostaglandin Synthesis Research Articles

Renal effects of angiotensin II: role of prostaglandins?

In the present study the possible role of endogenous prostaglandins in modulating the renal effects of angiotensin II was investigated in the isolated perfused rat kidney. Angiotensin II (5 ng/ml) caused both an increase in prostaglandin E2 synthesis and an increase in renal vascular resistance, as well as an increase in perfusate flow rate and glomerular filtration rate. Filtration fraction did not change. Inhibition of prostaglandin synthesis did not influence these effects of angiotensin II. In addition, angiotensin II caused natriuresis and to a lesser degree kaliuresis. These effects were independent of intrarenal hemodynamic effects. Inhibition of renal prostaglandin synthesis did not have any effect on the angiotensin-induced natriuresis. We conclude that the natriuretic effect of angiotensin II is independent of renal prostaglandin synthesis.

Renal prostaglandin E2 and F2?? synthesis during exercise

To assess the effects of acute exercise on renal prostaglandins E2 (PGE2) and F2 alpha (PGF2 alpha) synthesis, urine collections were obtained from six women before and after 30 min of treadmill exercise at approximately 80% of their maximal oxygen consumption. After receiving a placebo for 3 days, with acute exercise, there was a significant increase only in recovery urine PGE2 concentration. Due to a decline in urine volume, PGF2 excretion was unchanged and PGF2 alpha excretion was significantly decreased by exercise. Subjects repeated the tests after 3 d of indomethacin treatment (150 mg X d-1), a known renal prostaglandin (PG) inhibitor, and 3 d of sulindac (300 mg X d-1), a non-steroidal anti-inflammatory drug which may not inhibit renal PG synthesis. Pre-exercise urine PGE2 concentrations were decreased by indomethacin but not by sulindac, whereas, PGF2 alpha concentrations were decreased by both drugs. When compared to the control test, indomethacin and sulindac had different effects on pre-exercise urine/plasma osmolality ratios and free water clearances. Neither indomethacin nor sulindac influenced the decreases in free water clearances, which were observed during the placebo tests. Exercise proteinuria was significantly increased by indomethacin but not by sulindac. In conclusion, these data demonstrate that acute exercise may stimulate renal PGE2 synthesis. During exercise, renal PG synthesis attenuates protein excretion. There also appear to be differences between indomethacin and sulindac with regard to the effects on renal PG synthesis and kidney function.

Dexamethasone does not inhibit antidiuretic hormone-stimulated prostaglandin production in vivo.

Glucocorticoids are potent inhibitors of prostaglandin (PG) release in vitro, but they fail to influence basal PG production in vivo. To test one possible explanation for this apparent discrepancy in the present study we investigated the effect of dexamethasone (DEX) on basal and antidiuretic hormone-stimulated renal PG synthesis in vivo. In long term experiments, Brattleboro diabetes insipidus rats were treated with DEX (250 micrograms kg-1 day-1) for 7 days, and the effects of deamino-8-D-arginine vasopressin were investigated on the fifth day of DEX treatment. Administration of deamino-8-D-arginine vasopressin was accompanied by a marked increase in PGE2 and PGF2 alpha excretion in both control and DEX-treated animals, but the response was significantly higher during DEX treatment. Furthermore, DEX, by itself, caused a significant increase in the excretion of both PGs. In short term experiments, diabetes insipidus rats received a 24-h iv infusion of DEX (1 mg kg-1 day-1), then renal PG synthesis was stimulated acutely by the infusion of arginine vasopressin (AVP) for 40 min. DEX treatment failed to inhibit basal PG excretion, and the AVP-induced enhancement of PGE2 and PGF2 alpha production was also identical in control and DEX-treated animals. DEX was ineffective in altering the hydroosmotic effect of AVP, confirming that intrarenal PG synthesis was not inhibited. We conclude that glucocorticoids in vivo do not inhibit anti-diuretic hormone-stimulated PG production, and thus, a differential effect of glucocorticoids on basal vs. stimulated PG synthesis cannot account for the discrepancy between in vivo and in vitro studies.

Effects of gluco- and antiglucocorticoids on renal and aortic prostaglandin synthesis.

The effects of glucocorticoid agonists RU 26988 (G) and dexamethasone (D) and antagonist RU 486 (AG) on aortic and renal prostaglandin (PG) production were studied in Wistar rats. Blood pressure increased in rats administered G (20 mg X kg-1 X day-1) during 1 or 3 days; such increase was prevented by AG (100 mg X kg-1 X day-1). Renal papillary PGE2 release was increased after a 3-day administration of G, and this was prevented by AG. Neither G nor AG altered basal 6-keto-PGF1 alpha aortic production. However, G inhibited and AG magnified the stimulatory effect of ionophore A 23187, added in vitro, on 6-keto-PGF1 alpha production; AG reversed G inhibition. In addition, AG alone (20 mg X kg-1 X day-1 X 3 days) enhanced the stimulatory effect of angiotensin II (10(-8) M), added in vitro, on 6-keto-PGF1 alpha release. In vitro studies were performed on renomedullary interstitial cells grown in culture; G and D depressed PGE2 production in a dose-dependent manner; AG at equimolar 10(-8) M concentration inhibited this effect. In conclusion, AG inhibits the effects of G on blood pressure and PG synthesis. G exerts strong depressor activity on in vitro PGE2 renal production, whereas in vivo effects are more complex. Endogenous G inhibits aortic prostacyclin production, an action unmasked by AG administration. Diminished stimulation of vascular prostacyclin synthesis may contribute to vascular hyperreactivity in G-induced hypertension.

Cirrhotic ascites. Pathophysiology, diagnosis, and management.

Cirrhotic ascites occurs via both overflow and underfill mechanisms. Intrahepatic hypertension activates a hepatic baroreceptor reflex that enhances renal sodium absorption; plasma volume is expanded. As cirrhosis progresses, the hepatoportal Starling forces become sufficiently disturbed to sequester this "overflow" in the peritoneal cavity, which results in ascites formation. "Underfill" of the vascular system occurs and eventually dominates the clinical picture. Finally, intrahepatic hypertension also activates the renin-angiotensin system, which causes renal vasoconstriction; the increase in renal prostaglandin synthesis maintains renal blood flow. Although cirrhotic ascites is traditionally classified as a transudate, the serum-ascites albumin gradient may be a better indicator of ascites secondary to portal hypertension than other causes. General management of patients with cirrhotic ascites includes severe restriction of dietary sodium intake and bed rest; diuretics are added if spontaneous diuresis does not occur after 3 to 4 days.

Renal prostaglandin synthesis: Sites of production and specific actions of prostaglandins

Prostaglandins are substances that exert their effects at the site of their production. Therefore, the synthesis and effects of prostaglandins have to be considered separately for each nephron segment. In the cortex, major sites of prostaglandin synthesis include arteries and arterioles as well as the glomerulus. At these sites, prostaglandins are important in maintaining blood flow and glomerular filtration, especially during conditions of enhanced vasoconstrictor activity. Vasoconstrictors such as angiotensin II, norepinephrine, and vasopressin increase production of the vasodilator prostaglandins, thereby preventing an overshoot of their action. The role of arteriolar-glomerular prostaglandins in maintaining blood flow and filtration may be even more prominent during renal diseases. The proximal tubule and the loop of Henle show little ability to produce prostaglandins, but may generate considerable amounts of epoxygenase products of arachidonic acid. These epoxygenase products may play a prostaglandin-independent role in water and electrolyte transport in the thick ascending loop of Henle and the collecting tubule. Both the cortical and the medullary collecting tubules produce large amounts of prostaglandins, predominantly prostaglandin E 2 (PGE 2). In these segments, synthesis of PGE 2 is stimulated by bradykinin and to a somewhat more variable degree by vasopressin. The PGE 2 generated antagonizes the hydroosomotic effect of vasopressin both in vivo and in vitro, and may influence electrolyte excretion. Thus, the overall role of PGE 2—and possibly of epoxygenase products of arachidonic acid—in tubular functions seems to be one of local modulation of water and electrolyte transport. Finally, interstitial cells are a major site of medullary prostaglandin production. Prostaglandins generated by the interstitial cells may play a role in maintaining blood flow to this poorly oxygenated and hypertonic region of the kidney.

Prostaglandins in congestive heart failure and the effects of nonsteroidal anti-inflammatory drugs

With the failure of the heart as a pump, there ensues a series of neurohumoral compensations that defend organ perfusion at the expense of alterations in cardiac filling pressures and the distribution of blood flow to various regional circulations. Activation of the sympathetic nervous system and the renin-angiotensin II-aldosterone system and increases in circulating arginine vasopressin maintain arterial blood pressure by producing systemic arteriolar vasoconstriction and the renal retention of salt and water. Constriction of the efferent arterioles in the kidney by angiotensin II and norepinephrine promotes reabsorption of glomerular filtrate in the peritubular capillaries and maintains glomerular filtration in the face of declines in glomerular plasma flow and the glomerular permepbility-surface area ultrafiltration coefficient. In resting, sodiumreplete, conscious animals and humans, pharmacologic inhibitiop of renal cyclo-oxygenase by nonsteroidal anti-inflammatory drugs has little or no effect on renal hemodynamics. However, electrical or reflex stimulation of the renal nerves, intrarenal infusion of angiotensin II, or infusion of arginine vasopressin stimulates the release of vasodilator prostaglandins from the kidneys. In sodium-depleted animals or humans, and when cardiac output decreases, there is an increase in total peripheral vascular resistance but little change in renal vascular resistance. Increased renal synthesis of vasodilator prostaglandins (presumably by the blood vessels) maintains renal blood flow despite increased release of renin and norepinephrine from the kidneys. In these situations, pharmacologic inhibition of renal cyclo-oxygenase is accompanied by marked reductions in renal blood flow and glomerular filtration rate. When this occurs in patients with advanced heart failure, reversible oliguric renal failure may result. In this setting, cyclo-oxygenase inhibition may also increase arterial pressure and induce additional depression of cardiac function. Recent data indicate that blood vessels have the capacity to synthesize the sulfidopeptide leukotrienes C 4, D 4, and E 4, which can constrict peripheral and renal blood vessels and alter vascular permeability. The vascular cell types responsible for leukotriene C 4 synthesis and the potential roles of these vasoactive eicosanoids in kidney and other regional circulations are currently under study.

Renal function abnormalities, prostaglandins, and effects of nonsteroidal anti-inflammatory drugs in cirrhosis with ascites: An overview with emphasis on pathogenesis

The ability of the kidneys to excrete sodium and free water is often impaired in patients with cirrhosis. Sodium retention is a sine qua non for ascites formation. The impairment of water excretion causes hyponatremia and hypo-osmolality. In addition, these patients frequently have functional renal failure caused by intense renal vasoconstriction. The renin-angiotensin-aldosterone system and the sympathetic nervous system, which are activated in most cirrhotic patients with ascites, and a nonosmotic hypersecretion of antidiuretic hormone are important mechanisms of sodium and water retention. Angiotensin II and sympathetic nervous activity may also be involved in the pathogenesis of functional renal failure. The renal production of prostaglandins is increased in cirrhotic patients with ascites as a homeostatic response to antagonize the vascular effect of endogenous vasoconstrictors and the tubular action of antidiuretic hormone. Nonsteroidal anti-inflammatory drugs should, therefore, be administered with caution in these patients because they may induce acute renal failure and water retention. Although sulindac inhibits the renal synthesis of prostaglandins in cirrhotic patients with ascites, it appears to have less effect on renal function than do other nonsteroidal anti-inflammatory drugs administered to these patients.

Effects of nonsteroidal anti-inflammatory drugs in healthy subjects

Nonsteroidal anti-inflammatory drugs inhibit cyclo-oxygenase activity and thereby reduce prostaglandin synthesis. Studies in humans have used these cyclo-oxygenase inhibitors to examine the role of prostaglandins in controlling renal function. Although short-term studies have demonstrated reductions in effective renal plasma flow, glomerular filtration rate, urinary sodium excretion, and plasma renin activity, long-term administration of nonsteroidal anti-inflammatory drugs does not result in significant or clinically important changes in renal function in normal human subjects. If healthy volunteers are placed on low-sodium diets or treated with diuretics, both renal hemodynamics and salt and water excretion can become prostaglandin-dependent. Studies in normal subjects suggest that sulindac, a nonsteroidal anti-inflammatory drug that undergoes biotransformation in the kidney, does not inhibit renal prostaglandin synthesis or urinary sodium excretion under basal conditions but may impair furosemide-stimulated prostaglandin synthesis and changes in renal function. Doses of sulindac that spare basal renal cyclo-oxygenase do inhibit extrarenal cyclooxygenase. The mechanism responsible for this biochemical selectivity of sulindac is not related to a differential sensitivity of the renal cyclo-oxygenase to the active metabolite of sulindac, sulindac sulfide. Sulindac sulfide, in concentrations as low as 1 nM, was equipotent to indomethacin as an inhibitor of prostaglandin E 2 synthesis in primary cultures of three renal cell lines. Appropriate clinical use of all nonsteroidal anti-inflammatory drugs, including sulindac, requires careful consideration of risk factors that predispose to nephrotoxicity and careful monitoring when administered to patients at risk.

Antihypertensive Therapy With Triamterene-Hydrochlorothiazide vs Amiloride-Hydrochlorothiazide

Amiloride hydrochloride has now been recognized as a safe and effective potassium-sparing diuretic alternative to triamterene with a similar mechanism of pharmacologic activity. Studies were undertaken to assess the difference between therapy with the triamterene-hydrochlorothiazide combination (Dyazide) and an amiloride hydrochloride-hydrochlorothiazide combination (Moduretic) on renal prostaglandin production, since an increase in renal prostaglandin synthesis has been shown to mediate or enhance the pharmacologic action of certain diuretic drugs. Eight subjects treated for four weeks with triamterene-hydrochlorothiazide were compared with nine patients similarly treated with amiloride-hydrochlorothiazide. A 24-hour urine sample for prostaglandin E2 (PGE2) assay was collected under control conditions and after six weeks of therapy with either diuretic in all patients. The PGE2 excretion increased in the amiloride-hydrochlorothiazide-treated group; in the other group PGE2 excretion actually declined. It is concluded from these studies that therapy with amiloride-hydrochlorothiazide enhanced renal PGE2 production, whereas that with triamterene-hydrochlorothiazide actually decreased renal PGE2 production. This difference is an important renal consequence of the use of either drug and should be considered in the choice between these diuretic combinations.

Increased PGE2 excretion by dDAVP in humans depends on state of hydration.

The relationship of renal prostaglandin E2 (PGE2) excretion (UPGEV) to water deprivation, water diuresis, and subsequent antidiuresis by 1-desamino-8-D-arginine vasopressin (dDAVP) was studied in female volunteers. After 16 h of water deprivation, the subjects began a sustained water diuresis for 8 h. This diuresis caused a transient twofold rise in UPGEV at 2 h (P less than 0.05), which then fell back to or below baseline levels. dDAVP given during the water diuresis caused a transient rise of UPGEV as urine volume decreased and plasma osmolality fell from 277 +/- 1.5 to 271 +/- 2 mosmol/kg (P less than 0.01). Another group of subjects had the water diuresis discontinued after 4 h with dDAVP given at the 5th h when urine volume was decreasing and urine osmolality was increasing. In this setting dDAVP did not produce as great a fall in plasma osmolality nor did it increase UPGEV. These data indicate that renal prostaglandin synthesis (as determined by UPGEV) is increased transiently by an acute water load; dDAVP given during continued water ingestion results in a fall in plasma osmolality and increased PGE excretion; however, dDAVP does not increase UPGEV during normal hydration; and UPGEV is independent of changes in urine flow. These findings imply that renal prostaglandins may have a functional role in humans to inhibit the hydroosmotic actions of antidiuretic hormone, and thus hasten the excretion of a water load, and to prevent overhydration when inappropriate antidiuresis occurs. However, there is no evidence that the stimulus for prostaglandin production is dDAVP per se.

Effects of sulindac on renal function and prostaglandin synthesis in patients with moderate chronic renal insufficiency.

The renal effects of therapeutic doses of sulindac were studied in nine patients with stable renal insufficiency, mean creatinine clearance 37.0 +/- 2.2 ml min-1 1.73 m-2 (range 24.7-54.6 ml min-1 1.73 m-2). Nine days' treatment with sulindac produced a small, but significant, reduction in the mean creatinine clearance (37.0 +/- 2.2 to 34.7 +/- 2.2 ml min-1 1.73 m-2; P less than 0.02) and 99mTc diethylenetriaminepenta-acetate (DTPA) clearance (35.5 +/- 3.4 to 31.4 +/- 3.6 ml min-1 1.73 m-2; P less than 0.02) without altering body weight, effective renal plasma flow [131I]hippuran clearance), plasma renin activity (PRA), 24 h urinary volume or electrolyte excretion. After discontinuation of sulindac, creatinine clearance returned to pretreatment values. In five female patients, pretreatment urinary excretion of the 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), a stable breakdown product of prostacyclin (PGI2), was significantly reduced (P less than 0.02) when compared with four healthy controls, whereas prostaglandin E2 (PGE2) was unchanged. Administration of sulindac did not significantly alter the excretion rate of PGE2 or 6-ketoPGF1 alpha in this group of patients. In chronic renal disease with moderate renal impairment, reduced renal prostacyclin synthesis may be an important predisposing factor to the renal toxicity associated with the use of non-steroidal anti-inflammatory drugs (NSAID). Short term use of sulindac in therapeutic doses does not appear to influence the excretion of prostaglandins and produces only a minor reversible change in renal function; used cautiously it may have advantages over other NSAID in these patients.

Renal prostaglandins in cirrhosis of the liver.

Urinary prostaglandin excretion was studied in 42 patients with liver cirrhosis and in nine control subjects on restricted sodium intake and on bed rest. Creatinine clearance (CCr), sodium excretion (UNaV), plasma renin activity (PRA) and plasma aldosterone were also evaluated. Patients without ascites and ascitic patients without renal failure showed increased urinary excretion of immunoreactive 6-ketoprostaglandin F1 alpha (i6-keto-PGF1 alpha), prostaglandin E2 (iPGE2) and thromboxane B2 (iTXB2) when compared with controls, while immunoreactive PGF2a (iPGF2 alpha) levels did not differ from those in the control group. Patients with functional renal failure (FRF) presented a significant reduction of vasodilator prostaglandins but urinary excretion of iTXB2 was higher than in controls. On the whole, cirrhotic patients with higher urinary excretion of prostaglandins had normal or nearly normal PRA and aldosterone levels. i6-keto-PGF1 alpha and iPGE2 inversely correlated with PRA and aldosterone. The relationship between i6-ketoPGF alpha alpha and CCr was found to be highly significant in cirrhotic patients but not in the control group. On the other hand, iPGE2 significantly correlated with UNaV and with the fractional excretion of sodium (FENa). We concluded that: (a) enhanced renal prostaglandin synthesis in cirrhosis, inversely related to PRA and aldosterone, may be dependent on volume status; and (b) preserved renal function in these patients is associated with the ability to synthesize prostacyclin and PGE2.

Effect of salt loading on blood pressure and eicosanoid metabolism of spontaneously hypertensive rats fed a fish oil enriched diet.

This study investigated the effects of dietary modification of prostaglandin (PG) synthesis on blood pressure regulation in spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats under conditions of normal and elevated salt intake. After an initial period of 4 weeks on either a 2-series PG 'inhibitory' diet of fish oil (maxEPA) or a control diet of saturated fat, half of each group received 1.5% saline for 1 week. Blood pressures were unaffected by diet during the period of normal salt intake, but following salt loading, the maxEPA-fed SHR showed a blood pressure increase (mean = 21 mmHg) relative to the EPA-fed rats on water. Rats on maxEPA showed impaired ability to generate serum thromboxane and diminished excretion of urinary 6-keto-PGF1 alpha and PGE2. SHR on water showed greater serum TXB2 generating capacity than WKY, but diminished urinary PGE2 excretion. Thus, the increased blood pressure observed in the salt-loaded SHR on the maxEPA diet may be explained by reduced renal PG synthesis resulting in either mild sodium retention and/or increased vascular reactivity.

The effect of sodium intake on renal prostaglandin production.

The effect of chronic alterations in dietary sodium intake on renal arachidonic acid (AA) metabolism was studied in male Wistar rats who were maintained for 14 days on a diet consisting of sodium-deficient food and either deionized water (low salt intake, LSI), 1% saline (normal salt intake, NSI), or 2% saline (high salt intake, HSI). 24 h Urinary Sodium (UNaV) and plasma renin activity (PRA) measurements were shown to validate the dietary protocol. Microsomal preparations from the cortices and medullae were incubated with radiolabeled exogenous AA, and endogenous urinary prostaglandin (PG) levels were assayed by RIA to quantify renal PG synthesis. Cortical PGF2 alpha and PGE2 synthesis was found to be the greatest following LSI. In contrast, medullary PGF2 alpha was shown to be the least following LSI and to increase with increased sodium intake. Likewise, urinary PGF2 alpha levels significantly increased with increasing sodium intake. Changes in urinary PGE2 levels showed the same trend as PGF2 alpha but did not achieve statistical significance. These data show that dietary sodium differentially affects renal cortical and medullary PG synthesis and may reflect physiological differences in the regulation of cyclooxygenase in these zones. These data further suggest that the major source of urinary PGs is the renal medulla since the relationship of urinary levels to sodium intake mimics that described for the synthesis of PGs by the medullary tissue.

Inhibition of compensatory renal growth by indomethacin

Renal prostaglandins may be important in the modulation of compensatory renal growth. Reductions in renal mass are associated with increased synthesis of these substances by the remaining kidney, and inhibition of prostaglandin synthesis diminishes renal function in partially nephrectomized animals and in patients with reduced functioning renal mass. We examined the effects of uninephrectomy and treatment with indomethacin on renal prostaglandin E 2 and 6-keto prostaglandin F 1α concentrations in adult male Sprague Dawley rats. The renal content of these prostaglandins was significantly increased in the remaining kidney two days following uninephrectomy (p<0.01). Treatment with 5 mg/kg/day of indomethacin over this period abolished the compensatory increase in renal prostaglandin synthesis and significantly attenuated compensatory increases in renal mass, protein and RNA concentration (p<0.05). No alterations in kidney weight, protein or RNA concentrations were found in intact animals treated with the same dose of indomethacin. These findings suggest renal prostaglandins may participate in the biological events leading to compensatory renal growth.

Inhibition of renal prostaglandin synthesis in man: methodological and clinical implications.

Integrity of renal prostaglandin synthesis is necessary to maintain renal cortical and medullary function in patients with kidney, heart and liver disease. A comparison of the biochemical effects of various non-steroidal anti-inflammatory drugs (NSAIDs) necessitates that renal prostaglandin synthesis, as reflected by urinary immunoreactive prostaglandin excretion, be assessed with proper attention to problems created by seminal fluid contamination, inadequate chromatographic separation of samples, and largely unknown cross reactivities of systemic eicosanoid metabolites with antibodies raised against primary prostaglandins. Most, but not all, clinical studies support the observation that conventional doses of sulindac, administered orally, do not inhibit renal prostaglandin synthesis or alter renal function. Caution is in order, however, about the use of any NSAID, including sulindac at conventional dosage, in patients with severe liver disease as the plasma levels of sulindac sulfide are increased and prolonged compared to patients with normal hepatic function. Furosemide-induced natriuresis is probably not prostaglandin-mediated, in contrast to increased in renal blood flow and renin release. Some NSAIDs can attenuate the efficacy of antihypertensive therapy. Inasmuch as sulindac does inhibit systemic vascular prostacyclin production, its lack of hypertensive effect vis-a-vis other NSAIDs argues in favor of the importance of intrarenal prostaglandin-dependent mechanisms in mediating the hemodynamic effects of non-selective cyclooxygenase inhibitors.

Dissociation of hyperreninemia and renal prostaglandin synthesis in the adrenalectomized rat

The aim of this study was to determine whether hyperreninemia in the adrenalectomized (ADX) rat is dependent on renal prostaglandin synthesis, as has been suggested for two other hyperreninemic conditions, Bartter's syndrome and chronic liver disease. Plasma renin concentration (PRC) in anesthetized, ADX rats was significantly increased ( Δ +480%; p < 0.001) compared to sham-operated controls. In vivo , indomethacin (10 mg/kg i.v.) significantly reduced PRC of anesthetized, ADX rats after both 45 min ( Δ −34%; p < 0.05) and 90 min ( Δ −47%; p < 0.05). In vitro renin release from renal cortical slices of ADX rats was also significantly greater ( Δ +130%; p < 0.05) than from sham-operated control cortical slices. Renin release from cortical slices of ADX rats given dexamethasone (10 μg/kg/day) for 4 days prior to sacrifice did not differ from sham-operated control values. Prostaglandin E 2 (PGE 2) release from cortical slices of ADX rats did not differ significantly from controls. However, PGE 2 synthesis in glomeruli microdissected from ADX rats was significantly increased ( Δ +110%; p < 0.001) compared to controls. PGE 2 synthesis in glomeruli of dexamethasone-treated ADX rats remained significantly elevated compared to controls. Ibuprofen (10 −6 M) decreased PGE 2 synthesis in cortical slices by 80%. However, prostaglandin synthesis inhibition had no effect on renin release from either ADX or control renal cortical slices. These results suggest that despite increased glomerular synthesis, prostaglandins do not directly influence renin release in the ADX rat.

Effect of Sulindac on Prostaglandin Excretion and Renal Function in Cirrhotic Patients with Ascites

The effect of sulindac, a nonsteroidal anti-inflammatory drug, on renal prostaglandin synthesis and renal function variables was investigated in six cirrhotic patients with tense ascites and marked sodium retention. We studied serum thromboxane (TXB2) production, urinary prostaglandin excretion (6-keto-prostaglandin F1 alpha and TXB2) and renal function before and after administration of a therapeutic dose of sulindac (400 mg). After treatment, no significant changes were observed in urinary prostaglandin excretion, serum creatinine concentration, urine volume, or urinary sodium and creatinine clearance, whereas the serum TXB2 concentration was reduced in 89%. In five patients systemic prostaglandins were inhibited, but renal excretion remained unchallenged. However, one patient showed marked reduction of urinary prostaglandins associated with a depression of renal function. The study suggests that sulindac could be a safe substitute for other nonsteroidal anti-inflammatory drugs in cirrhotic patients with ascites. Further pharmacological trials seem to be warranted.

Effects of Intravenous Aspirin on Prostaglandin Synthesis and Kidney Function in Intensive Care Patients

The effects of intravenous acetylsalicylic acid (1.0 g bolus) on renal function and prostaglandin synthesis were evaluated in a prospective, controlled study in eight patients in an intensive care unit. Four of these patients had congestive heart failure. Administration of acetylsalicylic acid caused significant antidiuresis (-56%), antinatriuresis (-82%), renin suppression (-26%) and decreased GFR (-41%). All of these changes were completely reversible within 1-2 hours and tended to be more pronounced in the patients with congestive heart failure. Urinary excretion of prostaglandin E2 was depressed profoundly (-93%) and did not return to more than 45% of control 6 h after the administration of acetylsalicylic acid. We conclude that intravenous acetylsalicylic acid affects kidney function in a manner similar to other prostaglandin synthesis inhibitors. Its effects are, however, short-lived. The inhibition of urinary PGE2 excretion outlasts GFR depression, antidiuresis, antinatriuresis and renin suppression by several hours.