Effects of inhibition of prostaglandin-synthesis on renal electrolyte excretion and concentrating ability in healthy man

A comparison of the effects of ibuprofen and indomethacin upon renal haemodynamics and electrolyte excretion in the presence and absence of frusemide

1. This study has compared the effects of ibuprofen and indomethacin upon renal haemodynamics, electrolyte excretion and renin release in the presence and absence of frusemide under sodium replete conditions in eight healthy volunteers. 2. Neither ibuprofen (400 mg and 800 mg) nor indomethacin (50 mg) affected renal blood flow, glomerular filtration rate or electrolyte excretion in the basal state. 3. Frusemide had no effect on renal blood flow, but significantly increased glomerular filtration rate. This latter change was suppressed significantly only by ibuprofen 400 mg. Frusemide-induced diuresis was inhibited by all treatments, while natriuresis following frusemide was inhibited by indomethacin only. 4. Significant increments in plasma renin activity, which were suppressed by all treatments, were observed after frusemide. The degree of inhibition of the renin responses was significantly greater in the presence of indomethacin than with either dose of ibuprofen. 5. In a sodium replete setting in healthy volunteers, indomethacin and ibuprofen had no detrimental effects on basal renal function. In the presence of frusemide, indomethacin had more anti-natriuretic and renin-suppressing effect than ibuprofen. There was no evidence for a dose-related effect of ibuprofen.

Effect of prostaglandins on renal salt and water excretion

There are several important mechanisms by which renal prostaglandins modulate renal salt and water excretion. The role of endogenous renal prostaglandins in facilitating urinary sodium excretion and the individual nephron segments that are affected by renal prostaglandins are reviewed. The role of the administration of nonsteroidal anti-inflammatory agents on the kidney's ability to excrete salt and water both physiologically and clinically is summarized. The potential role for endogenous prostaglandins to antagonize the effect of antidiuretic hormone and to alter renal water excretion is also described. The clinical consequences of taking nonsteroidal anti-inflammatory drugs in terms of hyperkalemia, sodium retention with associated edema, and possible hyponatremia are all discussed. Although these clinical consequences are quite uncommon statistically, there are certain subsets of patients for whom additional concern is important.

[Hepato-renal syndrome (author's transl)]

The hepato-renal syndrome is defined as potentially reversible functional renal failure associated with acute fulminant hepatitis or, more often, with advanced chronic liver failure. It is characterized by oliguria, azotemia, retention of sodium and water with formation of ascites, and hyponatremia. While urinary sodium concentration of less than 10 mEq/l reflects intact tubular sodium absorption, the kidney lacks the ability for adequate free-water generation. This condition must be separated from specific renal diseases which may arise during the course of intra-or extrahepatic diseases and which must be classified accordingly. Pathophysiological aspects of the hepa-to-renal syndrome include hemodynamic factors, such as changes in intrarenal blood flow distribution in the presence of elevated intrarenal and reduced peripheral vascular resistance. The functional relationship of vasoconstrictor, sodium retaining, and anti-diuretic hormones (e.g., renin-angiotensin, aldosterone, and vasopressin) to vasodilator, diuretic, and natriuretic hormonal factors (e.g., prostaglandins, kinins, and natriuretic hormone) may be altered as well. Finally, a pre- and intrahepatic spillover resulting in decreased endotoxin clearance must be considered. Due to the lack of understanding of their complex interactions, so far pharmacological and therapeutic approaches remained ineffective to correct at least some of these factors. Today, recovery from hepato-renal syndrome will, therefore, mainly depend on the course of the underlying liver disease.

Effects of indomethacin on furosemide-stimulated urinary PGE2 excretion in man

We studied the effects of furosemide on urinary excretion of PGE2 and sodium and the effects of inhibition of prostaglandin (PG) synthesis with indomethacin or furosemide-induced PGE2 excretion and natriuresis in normal man. Furosemide (20 mg i.v.) increased the urinary excretion of PGE2 from 71.2 +/- 17.2 to 255.9 +/- 41.0 ng/4 h. Sodium excretion increased in parallel. Indomethacin, in a dose sufficient to decrease basal urinary PGE2 excretion by > 90%, significantly decreased both urinary PGE2 and sodium excretion under furosemide without affecting delivery of furosemide into the urine. The urinary excretion of furosemide was 9.4 +/- 0.4 and 9.3 +/- 1.4 mg/24 h with and without indomethacin, respectively. However, the furosemide-induced increment in PGE2 excretion correlated significantly with sodium excretion rate with and without indomethacin. Indomethacin changed the relationship between absolute amounts of furosemide in urine and PGE2 excretion but did not affect the increment in excretion over baseline or the significant correlation of urinary PGE2 with sodium excretion.

Prostaglandin-independent protection by furosemide from oliguric ischemic renal failure in conscious rats

In 38 conscious rats divided into seven groups, acute unilateral ischemic renal failure was induced by 1 hour of complete occlusion of the left renal artery while the contralateral kidney remained intact. Renal excretory function of the left kidney was monitored up to 144 hours after ischemia and revealed a typical course of oliguric renal failure with oligoanuria persisting for more than 48 hours. Urinary osmolality and sodium concentration became plasma isotonic after release of renal artery occlusion and approximated control values on day 6 after ischemia. In nine rats, the i.v. infusion of furosemide before (6 microgram/min/100 g body wt) and after (12 microgram/min/100 g body wt) renal artery occlusion protected the ischemic kidney from oligoanuria with endogenous creatinine clearance of 0.42 +/- 0.11 ml/min/g kidney wt 5 hours after ischemia. Tubular absorption of sodium and water was at least partially preserved 36 hours after ischemia when infusion of furosemide was stopped. The loop diuretic significantly (P less than 0.01) increased total urinary prostaglandin (PG) E2 excretion before and after renal artery occlusion; and 5 hours after ischemia, PGE2 excretion from the ischemic kidney significantly exceeded that from the intact kidney (P less than 0.05). Indomethacin (1 mg/100 g body wt) administered in six animals markedly suppressed control PGE2 excretion (P less than 0.05) as well as the furosemide-induced rise in urinary PG excretion before and after ischemia but did not modify the protective effect of the diuretic in this experimental model. Inhibition of PG synthesis, however, reduced urinary flow rate and sodium and potassium excretion of the contralateral intact kidney and almost completely prevented its compensatory rise in creatinine clearance. The results indicate that mechanisms other than the intrarenal prostaglandin system must be considered to mediate the protective effects of furosemide in acute ischemic renal failure.