Prostaglandin E2 Excretion Research Articles

Altered prostaglandin synthesis and impaired sodium conservation in the kidneys of old rats.

1. The aim of this investigation was to study the role of prostaglandins in the impaired Na+ conservation of the ageing kidney. 2. We measured the urinary excretion of thromboxane B2, 6-keto-prostaglandin F1 alpha and prostaglandin E2 in young (3-4 months) and old (20-21 months) rats after 12, 24 and 36 h of Na+ deprivation. In a separate protocol, we measured prostanoid synthesis by isolated glomeruli, cortical homogenates, medullary slices and papillary slices from young and old rats in basal conditions and after 15 days of dietary Na+ deprivation. 3. In the acute study, urinary excretion of 6-keto-prostaglandin F1 alpha and prostaglandin E2 decreased in young but not in old rats. Urinary excretion of prostaglandin E2 was lower in old rats, but did not vary significantly with Na+ deprivation. 4. In old rats, thromboxane B2 synthesis was increased in all the portions of the kidney except the medulla. Production of 6-keto-prostaglandin F1 alpha was elevated in glomeruli and tended to increase in the cortex. Prostaglandin E2 synthesis was also elevated in the cortex. Thromboxane B2 synthesis tended to increase in the medulla and was enhanced in the papilla. After Na+ deprivation, only glomerular prostaglandin E2 synthesis increased in young rats. In old rats, cortical and papillary synthesis of 6-keto-prostaglandin F1 alpha increased, whereas prostaglandin E2 synthesis did not change. 5. The results suggest increased thromboxane synthesis in the ageing kidney. Increased prostacyclin and prostaglandin E2 synthesis may be an attempt to counteract enhanced thromboxane production.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal kinin antagonism does not impair pressure-induced natriuresis.

We studied the contribution of the renal kallikrein-kinin system to short-term electrolyte and water balance during baseline and during acutely elevated renal perfusion pressure (RPP) in the anesthetized dog. Renal blood flow, glomerular filtration rate, urine flow rate, renin secretion rate, and urinary excretion of sodium, potassium, prostaglandin E2 (PGE2), and kinins were measured at baseline RPP during intrarenal infusion of 0.9% saline or the competitive bradykinin analogue [D-Arg0,Hyp3,Thi5,D-Phe7,Thi8]bradykinin (50 micrograms/min), which blocks vascular and interstitial kinin receptors. RPP was then raised above baseline (control group 25%; kinin analogue group 22%) by ligating the celiac artery, the superior mesenteric artery, and the aorta distal to the renal arteries. Renal parameters were again measured during infusion of saline or the kinin analogue. The analogue had no effect on renal hemodynamic or excretory parameters at baseline perfusion pressures. Increasing RPP significantly increased urine flow rates and urinary sodium excretion rates (control group, 43 mumol/min; kinin analogue group, 55 mumol/min) in both groups of animals. Increasing pressure also tended to decrease renin secretion rate in both groups of animals; however, neither increased pressure nor infusion of the analogue affected urinary excretion of PGE2 or kinins. The results suggest that intrarenal kinins are not powerful short-term regulators of electrolyte and water balance and that an intact kallikrein-kinin system is not necessary to induce pressure diuresis and natriuresis.

Prostaglandin E2 in renal transplant recipients.

The concentrations of prostaglandin E2 (PGE2), sodium, potassium and creatinine were determined in the blood and urine of 50 renal transplant recipients treated with cyclosporine A or azathioprine, as immunosuppressive agents, for at least one year post transplantation. Fourteen healthy subjects served as control group. The urinary PGE2 excretion was significantly decreased in all treated renal transplant recipients and this reduction was associated with significant decrease in urinary excretion of sodium and potassium. On the other hand, a high elevation in blood PGE2 concentration was observed while no significant changes were seen in sodium and potassium levels in the blood of these renal transplant recipients. The observations suggest an association between urinary PGE2 reduction and immunosuppressive treatments in renal transplant recipients; also, PGE2 may regulate intra-renal haemodynamics and influence the renal tubular electrolyte excretion. Moreover, urinary PGE2 can be used as an indicator of successful renal transplantation.

Influence of NSAID-induced inhibition of renal prostaglandin synthesis on inorganic sulfate clearance in rats.

The objective of the present investigation was to examine the influence of inhibition of renal prostaglandin synthesis on the renal clearance of inorganic sulfate, an electrolyte involved in the biotransformation of both exogenous and endogenous substrates. Homeostasis of inorganic sulfate is maintained predominantly by renal reabsorption in the proximal tubule. Using a crossover study design, the renal clearance of sulfate was assessed in conscious female Lewis rats during control periods and following the infusion of two structurally dissimilar nonsteroidal anti-inflammatory drugs, ibuprofen (IBU) and indomethacin (INDO). Animals were infused with IBU or INDO to achieve steady state concentrations of 59 +/- 8 micrograms/ml (mean +/- SD) of IBU and 22 +/- 3 micrograms/ml of INDO. At these serum concentrations, IBU and INDO produced greater than 80% decrease in the urinary excretion of prostaglandin (PG) E2. Treatment with either IBU or INDO significantly increased the renal clearance of sulfate, but did not alter the glomerular filtration rate as assessed by creatinine clearance. The role of prostaglandins in the effects of IBU and INDO on sulfate homeostasis was investigated by examining the influence of concomitant intraarterial PGE2 administration (infusion of 0.1 micrograms/min) on nonsteroidal anti-inflammatory drug-induced alterations in sulfate renal clearance. Although PGE2 alone did not significantly alter the renal clearance of inorganic sulfate or that of creatinine, the PGE2 infusion abolished the effects of IBU on sulfate renal clearance. Concomitant PGE2 administration also significantly increased the sulfate reabsorption rate in INDO-treated animals; other parameters were not significantly changed, although the fractional reabsorption of sulfate tended to increase (P = 0.17). The reason for the less pronounced effect on PGE2 on the INDO-sulfate interaction is as yet unknown, but may be partly due to additional mechanisms involved in the INDO-induced alterations in sulfate clearance. The results of these studies suggest that prostaglandin inhibition represents one mechanism whereby IBU can alter the renal clearance of inorganic sulfate.

Calcium homeostasis and hypercalciuria in hyperprostaglandin E syndrome

Children with hyperprostaglandin E syndrome, a neonatal variant of Bartter syndrome with enhanced renal and systemic formation of prostaglandin E2, have hypercalciuria, nephrocalcinosis, and osteopenia. Because prostaglandin E2 affects tubular calcium handling, stimulates the formation of calcitriol in vitro, and has osteolytic activity, we studied calcium homeostasis and the influence of prostaglandin E2 formation on hypercalciuria in nine patients with hyperprostaglandin E syndrome during long-term indomethacin treatment and after its withdrawal. Suppression of prostaglandin E2 formation by indomethacin resulted in improvement of biochemical and clinical features of hyperprostaglandin E syndrome. However, hypercalciuria, osteopenia, and nephrocalcinosis did not completely resolve. Despite a low calcium diet, daily urinary calcium excretion was enhanced during and after withdrawal of indomethacin treatment (median 6.3, range 5.3 to 14, and median 9.4, range 4.4 to 38 mg/kg per day, respectively). Daily urinary calcium excretion was greater after withdrawal than during indomethacin treatment. Urinary calcium excretion was not correlated with urinary prostaglandin E2 excretion. Plasma levels of intact parathyroid hormone (median 11, range 6.8 to 12 pmol/L) and calcitriol (median 157, range 108 to 236 pg/ml) were elevated during indomethacin treatment and decreased after withdrawal of indomethacin. These data suggest that hypercalciuria in hyperprostaglandin E syndrome is mainly due to a renal leak of calcium, which is caused by enhanced renal formation of prostaglandin E2 and a tubular defect not related to prostaglandin E2 formation. There is no evidence for prostaglandin-stimulated calcitriol formation. Decreasing plasma levels of parathyroid hormone in the presence of renal calcium losses after withdrawal of indomethacin treatment may be due to a bone resorption process caused by systemic prostaglandin formation; the process may contribute to hypercalciuria in the patient not receiving indomethacin.

Renal effects of angiotensin II inhibition during increases in renal venous pressure.

Increases in renal venous pressure have been shown to consistently increase renal interstitial pressure; however, not until renal interstitial pressure is increased threefold is a natriuresis noted in normal animals. Since the intrarenal angiotensin II (Ang II) concentration has been postulated to increase with increasing renal venous pressure, the antinatriuretic action of Ang II could override the natriuretic effect of increased renal interstitial pressure. Therefore, the role of Ang II in the natriuretic response to increased renal venous pressure was examined in 10 pentobarbital-anesthetized dogs. Mean arterial pressure, renal blood flow, renal interstitial pressure, glomerular filtration rate, urinary sodium excretion, plasma renin activity, and prostaglandin E2 excretion were measured at renal venous pressures of 3, 15, and 30 mm Hg. The measurements were repeated after the administration of captopril (1 mg/kg i.v. bolus, n = 5) or [Sar1,Ile8]Ang II (50 micrograms/kg i.v. bolus + 50 micrograms/kg/hr infusion, n = 5). Under control conditions, mean arterial pressure, renal blood flow, plasma renin activity, and prostaglandin E2 excretion remained unchanged when renal venous pressure was increased. The elevations in renal venous pressure increased renal interstitial pressure from 7 +/- 2 to 12 +/- 2 and 22 +/- 4 mm Hg, while sodium excretion remained unchanged until renal venous pressure was 30 mm Hg. In the captopril-treated group, increasing renal venous pressure increased renal interstitial pressure as under control conditions; however, sodium excretion (23 +/- 4, 19 +/- 4, and 27 +/- 6 mueq/min) was not significantly increased even at the highest renal venous pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of magnesium lithospermate B in rats with sodium-induced hypertension and renal failure.

To evaluate the antihypertensive effect of magnesium lithospermate B isolated from Salviae miltiorrhizae radix, determinations of blood pressure and urinary excretions of sodium, potassium, prostaglandin E2 (PGE2) and kallikrein, which have been proposed to play an important role in the regulation of blood pressure, were made in rats with sodium-induced hypertension and renal failure. In rats given magnesium lithospermate B, blood pressure was significantly decreased, whereas urinary excretion of electrolytes was significantly increased. Urinary PGE2 excretion following administration of magnesium lithospermate B increased as the dose of the compound was stepped up. The activity of kallikrein in urine was also increased by the treatment. From these results, the blood pressure-lowering action of magnesium lithospermate B may be due in part to enhancement of the kallikrein-prostaglandin system.

Effect of hypoxia on renal prostaglandin E2 production in human and rat neonates.

Effect of hypoxia on renal prostaglandin E2 (PGE2) production was shown in asphyxic newborn infants and experimental hypoxic rats. In asphyxic infants, at postnatal day 1, the urinary excretion of PGE2 in severe asphyxia (1.00 +/- 0.19 pg/kg/min, n = 10) was lower than that of the mild asphyxia (2.15 +/- 0.18 pg/kg/min, n = 10) or normal newborn infants (2.65 +/- 0.25 pg/kg/min, n = 8) (p less than 0.01). The urinary excretion of PGE2 was inversely correlated with the urinary N-acetyl-beta-D-glucosaminidase (r = -0.84, p less than 0.01). The urine volume in mild asphyxia (0.04 +/- 0.005 ml/kg/min) was higher in comparison to normal newborn infants (0.026 +/- 0.002 ml/kg/min) (p less than 0.01), but had no correlation with the urinary excretion of PGE2. In experimental hypoxic rats, the renal PGE2 concentration increased from 0.19 +/- 0.02 ng/mg protein to the maximum level of 0.59 +/- 0.03 ng/mg protein at 10 min of hypoxia. The renal PGE2 concentration then decreased to the minimum level (0.105 +/- 0.02 ng/mg protein) at 24 h after 20 min hypoxia. The renal ATP rapidly decreased during 20 min hypoxia, and gradually increased to 55.1 +/- 6.2 nmol/mg protein at 24 h after 20 min hypoxia, which recovered only about 60% of the control level. It seems likely that renal PGE2 does not play a major role in diuresis in mild birth asphyxia and that severe birth asphyxia suppresses the renal PGE2 production in early neonatal period.(ABSTRACT TRUNCATED AT 250 WORDS)

Magnesium Hydroxide

The mechanism by which Mg(OH)2 acts as a laxative is unknown. To explore the mechanism, six volunteers more than 55 years old, with normal bowel habits, were enrolled in a dose-response, randomized, placebo-controlled, double-blind, crossover design study. Each subject was studied for four inpatient periods of 5 days each on a metabolic ward with 9 days off of all medication between studies. In the hospital, all patients were on a diet fixed in calories, fluid volume, Na+, fiber, and Ca2+. At 8 p.m. on each study day, each subject took 45 ml containing either placebo or 1,200, 2,400, or 3,600 mg of Mg(OH)2 plus 240 ml of water. On the fourth and fifth hospital days of each period, 24-h stool output was quantified and analyses performed. Compared to placebo, Mg(OH)2 caused the following dose-dependent results: (a) increased number of bowel movements; (b) increased percentage of stool water; (c) increased stool volume; (d) increased stool Mg2+; and (e) increased total stool 24-h prostaglandin E2 (PGE2), with mean 24-h excretions as follow: placebo, 95 +/- 18 pg/24 h; 1,200 mg Mg(OH)2, 260 +/- 100; 2,400 mg Mg(OH)2, 357 +/- 117; and 3,600 mg Mg(OH)2, 525 +/- 196. There was a significant correlation between stool PGE2 excretion and stool water consistent with a causative relationship. However, the concentration of stool prostaglandin was lower than the concentration found to alter intestinal electrolyte transport in vitro. In summary, the laxative effect of Mg(OH)2 is associated with increased output of stool PGE2. The contribution of the stool PGE2 to the laxative effect of Mg(OH)2 is unknown.

Renal and hormonal effects and tolerance of an ANP analogue in healthy man

The effect of an analogue of atrial natriuretic peptide (P-ANP) on glomerular filtration rate (GFR), renal plasma flow (RPF), urinary flow rate, urinary sodium excretion, tubular function estimated by the lithium clearance technique, and plasma levels of sodium and water homeostatic hormones, has been studied in 40 healthy males. Placebo or P-ANP 0.3, 1.5, or 3.0 micrograms.kg-1 bwt were given as an intravenous bolus injection to different groups. P-ANP did not cause any immediate change in GFR or RPF, but significant dose-dependent increases in filtration fraction, urinary flow rate and urinary excretion rate of sodium were detected during the first 30 min after administration. Proximal absolute and fractional tubular reabsorption and distal absolute tubular reabsorption of sodium did not change after injection of P-ANP, while the distal fractional reabsorption of sodium was reduced in a dose dependent manner during the first 30 min. Plasma angiotensin II and aldosterone were significantly increased 30 and 150 min after dosage, whereas plasma atrial natriuretic peptide, plasma arginine vasopressin, and urinary excretion of prostaglandin E2 were unchanged. Cyclic guanosine monophosphate both in plasma and urine were increased in a dose-dependent manner. P-ANP cause a significant reduction in diastolic blood pressure and an increase in pulse rate. Two subjects had vasovagal syncope 30-60 min after injection of P-ANP. It is concluded that P-ANP has natriuretic, diuretic and hypotensive properties in healthy man.

Effects of short-term treatment with naproxen on kidney function in insulin-dependent diabetic patients with microalbuminuria

The renal effects of the prostaglandin synthesis inhibitor naproxen was investigated in eight patients with incipient type I diabetes nephropathy. The patients were treated with 1000 mg naproxen daily for 4 days in a placebo-controlled double-blind cross-over study. Naproxen reduced urinary prostaglandin E2 (PGE2) excretion by 60%, from 276 ng/24 h to 110 ng/24 h (P<0.05). Plasma renin activity (PRA) was reduced by 45% (F<0.05). Glomerular filtration (GFR) (single bolus 99mTc-DTPA technique) and effective renal plasma flow (ERPF) (131I-Hippuran clearance) were unchanged by naproxen. Microalbuminuria and renal albumin clearance was unchanged as was also urinary excretion of sodium, glandular kallikrein and β2-microglobulin (β2-M). Our results show that albumin excretion in incipient diabetic nephropathy is not solely dependent on the renal prostaglandin system. The difference in action between naproxen in this study and indomethacin in previous reports, could be caused by renal actions of indomethacin independent of the prostaglandin system.

Stimulating effects of atenolol on vasodepressor prostaglandin generation in spontaneously hypertensive rats.

1. To assess the role of the vasodepressor prostaglandin system in the antihypertensive properties of beta-adrenoceptor antagonist, we investigated the alterations of prostaglandin generation in the kidney and in the aorta when spontaneously hypertensive rats were treated with atenolol for 2 weeks. 2. The blood pressure reduction was associated with an increase in urinary sodium excretion and urinary prostaglandin E2 excretion. The sodium excretion was positively related to the prostaglandin E2 excretion. 3. Basal release of prostaglandin E2 from the sliced renal cortex was enhanced by the atenolol treatment. Prostacyclin-generating capacity in the aortic wall was also significantly increased. 4. Atenolol treatment stimulated prostaglandin synthesis in the kidney and vascular wall in a dose-dependent manner. However, atenolol per se did not directly stimulate prostaglandin synthesis in the vascular wall. 5. Inhibition of prostaglandin generation by a cyclooxygenase inhibitor, indomethacin, was associated with attenuation of the antihypertensive effects of atenolol. 6. Thus these data indicate that sub-chronic atenolol treatment stimulates vasodepressor prostaglandin generation in the kidney and in the aortic vessels, and this shares the antihypertensive effects of this drug with the mechanism of beta-adrenergic antagonism probably mediated through vasorelaxation and natriuresis.

Effects of tenoxicam on renal function and the disposition of inulin and p‐aminohippurate in healthy volunteers and patients with chronic renal failure.

1. The effects of tenoxicam on renal function were studied in 10 patients with chronic renal failure (creatinine clearance 46.7 +/- 11.9 ml min-1 1.73 m-2) and eight healthy volunteers. A parallel treatment control group of eight healthy volunteers received placebo. Tenoxicam was given orally in a dose of 40 mg daily for 2 days followed by 20 mg daily for a further 8 days. Renal function was assessed by measurement of the renal clearances of inulin and p-aminohippurate (PAH) using the single injection technique before and during administration of tenoxicam. 2. In the healthy volunteers there were no changes in glomerular filtration rate, effective renal plasma flow, or the urinary excretion of N-acetylglucosaminidase and beta 2-microglobulin on the 3rd and 10th days of treatment with tenoxicam. The mean urinary excretion of prostaglandins E2 and 6-keto F1 alpha decreased during treatment but there was great individual variation and the differences were not statistically significant. Tenoxicam had no effect on the half-life, clearance, volume of distribution or urinary recovery of inulin and PAH. 3. There was no significant change in the clearance of inulin and creatinine after treatment with tenoxicam for 10 days in the patients with chronic renal failure. However, in this group there was a significant increase in plasma creatinine on the 3rd and 6th days with a return to pretreatment levels by the 10th day. The administration of tenoxicam for 10 days was associated with a small but significant increase in the plasma half-life and volume of distribution of inulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of prostaglandin inhibition by indomethacin on plasma active and inactive renin concentration in men

The effect of inhibition of prostaglandin synthesis by indomethacin on active renin and on acid-activable inactive renin was studied in nine healthy, sodium-replete men, both at rest and exercise. These volunteers were investigated after pretreatment with placebo or indomethacin, 150 mg daily for 3 days. Indomethacin induced a decrease in active (p = 0.004), total (p less than 0.001), and inactive (p = 0.02) renin at rest recumbent on average by 42, 19, and 8%, respectively, and at rest sitting on average by 45, 15, and 3%, respectively. Inhibition of prostaglandins with indomethacin reduced (p less than 0.001) active and total renin at each level of work load but not (p = 0.32) inactive renin. However, the exercise-induced stimulation (p less than 0.05) of active and total renin still occur during indomethacin. Indomethacin reduced (p less than 0.001) at rest sitting and at maximal exercise the plasma concentrations of immunoreactive prostaglandins E2 by 50 and 54%, respectively, prostaglandin F2 alpha by 36 and 39%, respectively, and 13,14-dihydro-15-keto-prostaglandin F alpha by 38 and 60%, respectively. The urinary excretion of immunoreactive prostaglandin E2 and F2 alpha was also reduced.

Nifedipine Increases Urinary Excretion of Prostacyclin Metabolite in Hypertensive Pregnancy

Renal prostanoid excretion was investigated in nine hypertensive pregnant patients before and during treatment with nifedipine 10 mg orally t.i.d. Urinary excretion of prostacyclin (measured as 6-ketoprostaglandin F1 alpha, 6-keto-PGF1 alpha) increased by 77% during nifedipine treatment (P less than 0.05). No changes were found in prostaglandin E2 (PGE2) and thromboxane A2 (as thromboxane B2, TXB2) excretions. A significant reduction in blood pressure did not correlate with an increase in 6-keto-PGF1 alpha excretion. Plasma prekallikrein and urinary kallikrein and catecholamine excretions remained unaltered. In six normotensive non-pregnant women, increase in 6-keto-PGF1 alpha excretion during nifedipine treatment was not significant. No changes in PGE2 and TXB2 excretions were found, whereas plasma prekallikrein was reduced (P less than 0.05) and urinary excretion of kallikrein (P less than 0.05) and noradrenaline (P = 0.06) increased under nifedipine. The results suggest that nifedipine enhances the renal 6-keto-PGF1 alpha excretion in hypertensive pregnancy.

Contribution of Prostaglandins to Pressure Natriuresis in Dahl Salt-Sensitive Rats

To examine the role of prostaglandins on pressure natriuresis in Dahl salt-sensitive (DS) rat, the pressure-natriuresis relationships in DS and Dahl salt-resistant (DR) rats were characterized with or without indomethacin (2 mg/kg/h) by utilizing an in vivo renal perfusion study. When untreated, in the DS rat the pressure-natriuresis curve was blunted (P less than .05) and excretion of prostaglandin E2 (38 +/- 11 to 109 +/- 43 pg/min) was decreased in comparison to the DR rat. With indomethacin, the pressure-natriuresis curve in the DR rat was blunted, while no significant changes were observed in the DS rat. Plasma renin activity and concentration of atrial natriuretic peptide were not changed by the treatment of indomethacin in both strains. These results suggest that the decrease in renal prostaglandins, at least in prostaglandin E2, plays some role in blunting pressure natriuresis in DS rat.

Role of Endothelium-Derived Relaxing Factor in Endothelin-Induced Renal Vasoconstriction

It has been suggested that endothelin (ET) induces the release of endothelium-derived relaxing factor (EDRF). To explore the possible modification of ET-induced renal vasoconstriction by EDRF, we examined the effects of ET on renal vascular resistance (RVR) and urinary Na excretion (UNaV) in the rat isolated perfused kidney before and after the administration of EDRF antagonists. ET at 2 x 10(-11) to 2 x 10(-9) M elevated the RVR in a dose-dependent fashion, whereas it lowered the RVR at 10(-12) M. ET decreased UNaV significantly only at the highest dose. Acetylcholine at 10(-7) M decreased the RVR (-19%, p less than 0.05) and increased UNaV (+177%, p less than 0.05). In contrast, a soluble guanylate cyclase inhibitor, methylene blue (MB; 10(-5) M), increased the RVF by 30% (p less than 0.05) and decreased UNaV by 48% (p less than 0.05). Pretreatment with MB significantly augmented the ET-induced renal vasoconstriction by about 80%. However, UNaV was not influenced significantly. ET increased the urinary excretion of prostaglandin (PG) E2 and 6-keto-PGF1 alpha. Pretreatment with indomethacin (10(-5) M) also significantly enhanced the response of RVR to ET by 60% without changing UNaV. These results suggest that the vasoconstrictor, but not the antinatriuretic, activity of ET may be modified by the release of EDRF and prostacyclin.

Effects of Arginine Vasopressin on Blood Pressure and Renal Prostaglandin E2 in Rabbits.

The role of arginine vasopressin (AVP) in blood pressure regulation in humans and animals is still controversial. The present study was designed to investigate the effects of AVP on blood pressure and the excretion of sodium and prostaglandin (PG) E2 in rabbits. AVP dissolved in 0.01 M acetic acid was infused subcutaneously at a rate of 0.86 ng/kg/min with a miniosmotic pump into 12 New Zealand white rabbits (2.7-3.4 kg), while 10 controls were given vehicle alone. AVP infusion resulted in a 3.5-fold rise in the level of plasma AVP (21.8 +/- 4.4 (SEM) pg/ml) as compared with controls, associated with a significant decrease in the urine volume and urinary excretion of sodium. The PGE2 excretion was increased 1.8-fold after AVP infusion. In the chronic AVP-infused group, blood pressure was not significantly increased, but the acute vascular response to AVP was significantly attenuated without any changes in the vasopressor response to angiotensin II. Preadministration of V1-antagonist completely abolished the vasopressor action of AVP, but not that of angiotensin II, in either group. These results suggest that circulating AVP within physiological range of concentrations may stimulate renal PGE2 synthesis and attenuate the vascular response through vascular V1 receptors without affecting the baroreflex, which may be attenuated through V2 receptors.

腹水を伴う肝硬変患者における腎機能障害―ANP静注負荷およびIithium clearance法による臨床的検討―

Synthetic alpha-human atrial natriuretic peptide (alpha-hANP), 1 micrograms/kg, was intravenously given to 16 cirrhotic patients with ascites and 9 control subjects (CS) to investigate major factors responsible for sodium retention and refractory ascites. The following parameters were measured before and after alpha-hANP administration; such as lithium clearance (CLi) as an index of fluid delivery to the distal tuble, mean arterial pressure (MAP), urinary sodium excretion rate (UNaV), urine volume (V), glomerular filtration rate (GFR), effective renal plasma flow (ERPF), plasma renin activity (PRA), plasma aldosterone concentration (PAC), urinary excretion of prostaglandin (PG)E2, 6-keto-PGF1 alpha (6-k-PGF1 alpha), and thromboxane B2 (TxB2). Patients were divided following alpha-hANP administration into 2 groups as "good responders (GR)" and "poor responders (PR)", in which GR was defined as the group showing 2-fold-increase in UNaV. In contrast, PR had significant lower MAP (71.8 +/- 5.04 mmHg), GFR (21.3 +/- 3.90 ml/min), ERPF (158.0 +/- 43.8 ml/min), FELi (CLi/GFR; 12.6 +/- 1.26%), and higher PRA (8.72 +/- 0.99 ng/ml/h) and PAC (12.2 +/- 3.13 ng/dl) than GR. GR demonstrated almost same natriuretic response as CS with an increase of GFR and renal PGs synthesis, and a decrease of FELi despite reduction in blood pressure. However, alpha-hANP did not suppress PRA, PAC, and distal tubular reabsorption of sodium (FDRNa = 1-FENa/FELi) in cirrhotic patients, whereas suppressed in CS. UNaV correlated with FELi (r = 0.687, p = 0.01) and GFR (r = 0.777, p = 0.01). PRA correlated with FELi r = 0.669, p = 0.015), GFR (r = -0.634, p = 0.018), and MAP (r = 0.858, p = 0.001) only in cirrhosis. These results therefore indicated that hypotension caused by hemodynamic alteration and extremely stimulated renin release might effect on proximal tubular sodium reabsorption and GFR, leading to sodium retention and diuretic resistance in cirrhosis.

Long-term Effects of Delapril on Renal function and Urinary Excretion of Kallikrein, Prostaglandin E2, and Thromboxane B2 in Hypertensive Patients

The effects of delapril, an angiotensin converting enzyme (ACE) inhibitor, on renal function and the renin-angiotensin and kallikrein-prostaglandin systems were investigated in 10 hypertensive patients who were treated for between 4 months and 1 year. There was a significant (P less than .05) increase in renal blood flow (RBF) without affecting glomerular filtration rate. Filtration fraction increased, while renal vascular resistance decreased. There were also significant (P less than .05) increases in urinary kallikrein and prostaglandin excretion, while thromboxane excretion decreased. There was no change in urinary aldosterone excretion. These results suggest that renal hemodynamic changes seen during long-term therapy with delapril are caused, in part, by activation of the kallikrein-prostaglandin system, as well as suppression of the renin-angiotensin system.