Antidiuretic response in conscious dogs following peroral administration of arginine vasopressin and its analogues

Conscious dogs were subjected to a constant water load causing water diuresis. When arginine vasopressin or analogues of vasopressin were administered through a gastric tube a dose-dependent antidiuretic response occurred. All the peptides tested proved to be antidiuretic in doses of 50 micrograms or less with 1-deamino-8-D-arginine vasopressin and 1-deamino-4-asparagine-8-D-arginine vasopressin being the most potent substances. No pressor response was observed even after 1 mg of AVP.

[Effect of ajmaline on kidney function]

Ajmaline increases diuresis and excretion of sodium in rats (10 mg/kg subcutaneously) and in dogs (3 mg/kg intravenously) at the expense of elevation of the glomerular filtration rate and renal blood flow. Ajmaline produces no direct effect on sodium potassium or water transport in renal tubules.

[Effects of several beta-blockers and penfluzide, a thiazide diuretic, on the blood pressure, urinary water output and excretion of Na and K in DOCA-saline-induced hypertension in rats]

Effects of beta-blockers on the blood pressure (BP), urinary output (V) and excretion of Na% (UNaV) and K+ (UKV) were studied in DOCA-saline hypertensive rats in comparison with those of a thiazide diuretic drug, penfluzide. Pindolol produced a hypotension at all infusion rates of Ringer's solution used and a decrease in V with a retention of Na+ and K+ at a low infusion rate. There was a parallel shift of Guyton's renal function curve back to the lower pressure ranges. Similar effects were observed with labetalol. Propranolol induced an increase in UKV at all infusion rates and had a diuretic action at a high infusion rate without producing a significant fall of BP. UKV tended to be increased after atenolol, with essentially no change in other parameters. A new beta-blocker with alpha-blocking action, K-351, produced a hypotension at intermediate and high infusion rates and an increase in UNaV (low infusion rate) and UKV (low and high rates). UKV tended to be increased with another new beta-blocker, N-696, with a fall of BP at high infusion rate. Penfluzide produced a significant decrease in BP at intermediate and high infusion rates and an increase in UKV at all infusion rates.

Effects of atrial natriuretic factor on renal handling of water and electrolytes in rats

The intravenous injection of an extract of atrial myocardium into anesthetized rats during a hypotonic diuresis resulted in an increase in the renal excretion of water, sodium, potassium, calcium, magnesium, and phosphate. There was an increase in urine concentration which was probably a result of the secretion of vasopressin since it did not occur in Brattleboro (di/di) rats. A transient increase in glomerular filtration rate and renal plasma flow occurred during the first five minutes with a more sustained rise in filtration fraction. Injection of atrial extract also caused a partial inhibition of solute-free water formation in Brattleboro rats subjected to water diuresis and a partial inhibition of solute-free water reabsorption in rats subjected to maximal antidiuresis by infusing vasopressin. In neither case was the degree of inhibition as profound as that observed after injecting furosemide in a dose which caused a comparable natriuretic response. A large dose of furosemide blocked the natriuretic response to atrial extracts whereas, when a comparable level of sodium and water output was produced by massive infusions of saline, the natriuretic response to atrial extract was increased. It is suggested that atrial natriuretic factor might inhibit sodium transport in nephron segments beyond the medullary thick ascending limb. Furosemide might also act at the same tubular site or inhibit tubular secretion of the atrial natriuretic factor.

Effect of ethanol on the pharmacokinetics of penicillin in the rat

The effect of a single intraperitoneal dose of ethanol (2 g/kg) given 30. min. prior to intravenous administration of benzylpenicillin (20, 40 and 80 mg/kg) was studied in rats. Ethanol pretreated animals showed lower blood and brain tissue levels of penicillin, 15 and 30 min. after the administration of the two lower penicillin doses. This difference was not observed when the penicillin dose was raised to 80 mg/kg. The quotient between brain and serum concentrations was increased 45 min. after the injection of 20 mg/kg of penicillin. Urine collection during the following 2 days showed an increased urine volume during the first 4-hour period in animals pretreated with ethanol. During the same time period they excreted less benzylpenicillin than the controls.

Aldosterone suppression with dopamine infusion in low-renin hypertension

A dopaminergic mechanism has been proposed to suppress aldosterone secretion. To assess the possibility that a defect in the dopaminergic mechanism might enhance aldosterone secretion in hypertensive patients, we determined basal and adrenocorticotropic hormone (ACTH)-stimulated plasma aldosterone (PA), cortisol, renin activity, and potassium concentrations before and during dopamine receptor stimulation with dopamine infusion and bromocriptine administration and dopamine receptor blockade with metoclopramide. The patient study groups included: (a) seven patients with low-renin hypertension and abnormal aldosterone suppression with sodium loading and presumed bilateral zona glomerulosa hyperplasia (ZGHP); (b) two patients with aldosterone-producing adenoma; (c) five patients with low-renin hypertension but normal aldosterone suppression with sodium loading; and (d) six patients with normal-renin hypertension. Dopamine infusion in patients with ZGHP caused PA to fall (P less than 0.01) into the normal range, but did not block the enhanced (P less than 0.05) aldosterone response to ACTH that is characteristic of these patients. Dopamine infusion in patients with low-renin hypertension but normal aldosterone suppression also suppressed PA (P less than 0.01), whereas it had no effect upon PA in patients with normal-renin hypertension or aldosterone-producing adenoma and did not blunt the PA response to ACTH in either group. Bromocriptine administration had no effect upon basal or ACTH-stimulated PA. Dopamine infusion in patients with ZGHP also enhanced (P less than 0.05) diuresis and natriuresis in comparison with normal-renin patients. Metoclopramide administration increased (P less than 0.01) PA in all patients. Thus, a dopaminergic mechanism appears to be important in the regulation of aldosterone secretion in patients with ZGHP and in other low-renin hypertensives with normal aldosterone suppression with sodium loading. In contrast, this latter group does not exhibit an enhanced aldosterone response to ACTH. Both of these groups differ from normal-renin hypertensives, who have no PA suppression with dopamine infusion.

A new oral renal vasodilator, fenoldopam

Fenoldopam, a dopamine agonist, was evaluated in renal clearance studies during water diuresis after oral doses of 25, 50, and 100 mg. After the 100-mg dose there was an increase in urine flow rate, paraaminohippurate clearance, free water clearance, and an increase in the fractional excretion of sodium, calcium, and uric acid. These effects were evident within the first hour, peaked during the second hour, and lasted about 3 hr. Doses of 50 and 25 mg induced smaller increases. There was no significant change in inulin clearance at any dose. To elucidate the mechanism of action, the studies were repeated after treatment with a dopamine-receptor antagonist (metoclopramide). Metoclopramide greatly diminished the renal effects of fenoldopam. These findings indicate that fenoldopam is an active renal vasodilator in man and increases urine volume, free water clearance, and fractional excretion of sodium by stimulation of renal dopamine receptors.

5-sulfamoylorthanilic acids, a sulfonamide series with salidiuretic activity

A series of 4,N-disubstituted 5-sulfamoylorthanilic acids was synthesized by nucleophilic substitution reactions starting either from 2,4-dihalogeno-5-sulfamoylbenzenesulfonic acids or, in most cases, from phenyl 2,4-dihalogeno-5-sulfamoylbenzenesulfonates. The latter method is based on the relative stability of the phenoxysulfonyl group to nucleophiles, e.g., amines, phenols, and thiols, and the possibility of smooth hydrolytic or hydrogenolytic cleavage as a final step, with formation of the SO3H group. On evaluation of these compounds for salidiuretic activity in rats orally (po), and in dogs orally and intravenously (iv), a number of highly active substances was found; the best had a threshold dose of 0.02 mg/kg po in dogs. The results are given in tables, and the structure-activity relationships within the series are discussed. Besides the known effect of the phenoxy radical, an outstanding activating effect was shown by the butylsulfonyl and cycloalkylsulfonyl radicals and by the N-methylanilino radical in particular when they were located in the 4-position of the orthanilic acid molecule. The sulfanilic acid isomers corresponding to three of the most active compounds were synthesized and proved to be completely inactive in rats.

Single-dose i.v. Aldactone for congestive heart failure: a preliminary observation

Aldactone (200 mg potassium canrenoate i.v.) was given in a single dose as the sole drug to 30 patients with congestive heart failure (CHF). Of these patients 21 were unresponsive to routine treatment. Clinical improvement was observed in 18 of 30 patients (60%) within 6 h after Aldactone injection. Good diuretic effect (urine volume over 500 ml/6 h) was achieved in 14 patients, including 7 cases who responded dramatically (diuresis 700-1500 ml in 6 h). Plasma aldosterone concentrations before the injection of Aldactone were variable in individual patients. An analysis of their diuretic response to the Aldactone injection within 6 h showed that responders had significantly higher initial plasma aldosterone level (312 +/- 108 pg/ml) than non-responders (152 +/- 31 pg/ml) (p less than 0.02). The same tendency was observed if good or poor clinical effects were considered. Aldactone caused a slight increase in plasma potassium level (0.20 mEq/1) (p less than 0.025). Aldactone given in a single dose i.v. to patients with CHF is a potent drug and can produce a dramatic response in some individuals who are refractory to routine therapy. The beneficial effects of Aldactone could be seen within the first 6 h especially in patients with secondary aldosteronism.

[Effect of dopamine on transport of organic substances in dog kidneys]

I. v. infusion of dopamine increased diuresis, glomerular filtration rate, maximal reabsorption of glucose and tubular secretion of cardiotrast. Infusion of dopamine into the renal artery did not affect glomerular filtration rate and tubular secretion of cardiotrast while maximal reabsorption rate of glucose was increased. Dopamine exerted some direct effect on the transport of glucose, which effect can be blocked with haloperidol.

Role of renin release in the hemodynamic, renal and dipsogenic actions of the prostacyclin analogue CG 4203 in conscious rats

The influence of CG 4203, a chemically and metabolically stable prostacyclin analogue, on plasma renin activity, arterial blood pressure, renal function and water intake was investigated in conscious rats. CG 4203 infused intravenously starting at 1 microgram X kg-1 X min-1 induced both a fall in blood pressure and an increase of plasma renin activity. The angiotensin II antagonist saralasine infused simultaneously intensified the hypotensive effect of CG 4203 (1.0 microgram X kg-1 X min-1). Within a similar dose range CG 4203 dose-dependently inhibited diuresis and saluresis and reduced the urinary sodium/potassium ratio. These effects were partially reversed by adrenalectomy and completely abolished by pretreatment with the angiotensin I converting enzyme inhibitor captopril. Similarly, CG 4203 (0.21 - 4.64 micrograms X kg-1 X min-1) dose-dependently caused increased water intake which was prevented by previous nephrectomy. In conclusion, it is demonstrated that CG 4203 like prostacyclin itself already at hypotensive threshold dosages stimulates a functionally relevant renin release. The activation of the renin-angiotensin-aldosterone system attenuates the intrinsic hypotensive effects of CG 4203. the antidiuretic and dipsogenic efficacy of CG 4203 can also be attributed to renin-dependent angiotensin II formation.

Terbutaline infusion in cardiogenic shock: acute hemodynamic effects and clinical response

The effect of terbutaline infusion was studied in six patients with cardiogenic shock due to acute myocardial infarction. Terbutaline was initiated at 3 micrograms/kg/min, and the subsequent infusion rate was adjusted according to heart rate and blood pressure. At 3 hours after infusion arterial pressure increased from 62 +/- 13 mm Hg (mean +/- S.D.) to 89 +/- 13 mm Hg (P less than 0.001), cardiac index increased from 1.38 +/- 0.29 liter/min/m2 to 2.68 +/- 0.47 liter/min/m2 (P less than 0.001), and heart rate increased from 92 +/- 32 beats/min to 112 +/- 29 beats/min (P less than 0.005). Pulmonary artery wedge pressure fell from 24 +/- 7 mm Hg to 17 +/- 3 mm Hg (P less than 0.01), right atrial pressure fell from 12 +/- 4 mm Hg to 6 +/- 3 mm Hg (P less than 0.005), and systemic vascular resistance fell from 1880 +/- 641 dyn-sec/cm5 to 1515 +/- 418 dyn-sec/cm5 (P less than 0.05). In addition, urine flow increased from 4 +/- 6 ml/hr to 314 +/- 237 ml/hr (P less than 0.05), and subjective improvement was noted in all subjects. Undesirable effects observed were hypokalemia (all subjects), supraventricular tachycardia (one subject), and ventricular ectopic beats (three subjects), which responded to potassium replacement and other treatments. All patients required prolonged maintenance infusion to maintain adequate hemodynamic and clinical response. Four patients were weaned off from maintenance therapy after a mean duration of 4.8 days and eventually were discharged from the hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of an angiotensin II antagonist, saralasin, given before donor nephrectomy, on kidney function after transplantation. A controlled prospective study

Kidneys from cadaver donors who had been treated during the last 10 min before bilateral nephrectomy with an infusion of 10 micrograms/kg-1/min-1 (Sar1, Val5, Ala8)-angiotensin II had a remarkable, significantly lower percentage of acute renal failure (25%) after renal transplantation than untreated kidneys (58.3%). Anuria was seen in the treated group only in 4.2%, although it occurred in the untreated control group in 16.6%. The role of the activated renin-angiotensin system in postischemic acute renal failure is discussed.

Beneficial effects of verapamil on postischemic renal failure

The effects of calcium blockade with verapamil on postischemic renal failure were tested in dogs. Two experiments were performed. In experiment 1 (n = 7), one kidney in each dog received an infusion of verapamil and the other received saline for 30 minutes prior to induction of 1 hour of ischemia. Inulin clearance (CIN), urine flow, and renal blood flow (RBF) were measured. Infusion of verapamil increased urine flow from 0.99 to 4.29 ml/min (P less than 0.001). CIN and RBF did not change significantly nor did urine flow in the saline-treated kidney. Three hours after ischemia there was no significant difference in CIN, although it was lower in verapamil-treated kidneys. RBF declined in both treatments. In experiment 2 (n = 6) kidneys were treated with verapamil and saline for 50 minutes beginning immediately after 1 hour of ischemia. Urine flow and CIN were significantly higher in verapamil-treated kidneys during the infusion (3.09 +/- 0.44 versus 0.26 +/- 0.12 ml/min, P less than 0.001; 28.6 +/- 7 .4 versus 6.2 +/- 3.1 ml/min, P less than 0.025, respectively). CIN remained elevated in verapamil-treated kidneys at 3 hours, however RBF was depressed in both verapamil- and saline-treated kidneys. These results suggest that verapamil is a potent diuretic and that verapamil can be given after renal ischemia with significant attenuation of postischemic renal failure.

Cardionatrin I - a novel heart peptide with potent diuretic and natriuretic properties

Rat atrial muscle extracts are able to induce a powerful diuretic and natriuretic response. In the present work it was found that when rat atrial extracts are subjected to reverse phase-high pressure liquid chromatography, diuretic and natriuretic activities are recovered in four distinct chromatographic regions. From one of these chromatographic regions we purified to chemical homogeneity a peptide referred to as "Cardionatrin I" which has potent diuretic and natriuretic properties. Amino acid analysis showed that cardionatrin I has 49 residues, including one cystine, and a molecular weight of 5,499. Yield of cardionatrin I was 12-20 nmole per 1,000 atria. Injection of 0.5 nmole induced a characteristic diuretic and natriuretic response in the non-diuretic assay rat.

Furosemide fails to alter plasma active or inactive renin in conscious sheep but does so in anaesthetized animals

Regulation of plasma levels of active and inactive renin was investigated using sheep with indwelling artery, vein and bladder catheters. Control and experimental studies were carried out in the same animals on different days. Volume depletion during any single experiment was limited to a maximum of 50 ml. Despite large changes in sodium and water excretion, the diuretic furosemide at two dose levels, 1 and 10 mg/kg, failed to alter plasma levels of either active or inactive renin in conscious sheep. Induction of pentobarbitone anaesthesia in the sheep did not, per se, alter either plasma active or inactive renin. Furosemide (10 mg/kg) in anaesthetized animals produced a similar diuresis and natriuresis response to conscious sheep, but plasma active renin increased by 270% and inactive renin decreased to zero. In conscious sheep given an infusion of papaverine, furosemide also produced an increase in plasma active renin and a concurrent decrease in the inactive form. In both anaesthetized animals and in conscious sheep infused with papaverine, furosemide-induced intrarenal vasodilation, as evidenced by changes in clearance of p-aminohippuric acid, was much reduced in comparison to the conscious animals. This may be significant in relation to the control of renin secretion. It appears that the macula densa sodium receptor, which is considered to regulate renin release, will only function after it has been primed by other intra- or extrarenal factors. This is discussed, particularly in relation to the possible role played by the prostaglandin system.

Influence of prostaglandin A1 on renal filtration, hemodynamics and excretion. Investigations in chronically instrumented conscious dogs on a low- and high-sodium diet

The effect on renal function of a 210-min infusion of PGA1 into the aorta of 10 conscious beagle dogs has been investigated. In the sodium-replete group, PGA1 caused an increase in the glomerular filtration rate (GFR) (24%), renal blood flow (17%) and sodium excretion (20%). By contrast, in the sodium-depleted group, PGA1 caused a considerable reduction of GFR (25%) and sodium excretion (51%). In this group, baseline renal blood flow was lower, and there was no further reduction during PGA1 infusion. Fractional sodium excretion was unchanged in the sodium-replete dogs, but was reduced in the sodium-deplete state. Plasma renin activity was markedly elevated and further increased in the sodium-deplete group, but it was nearly unchanged in the sodium-replete group. This difference in renal response to exogenous PGA1 might be due to interaction with the renin-angiotensin system, which was markedly stimulated by sodium depletion and additionally by prostaglandin infusion.

Calcium blockade in arterial hypertension. Review

The use of calcium blockers in arterial hypertension is based on experimental evidence for an altered role of calcium (Ca++) in hypertensive vascular smooth muscle and enhanced vasodilatatory effects of these drugs in the hypertensive organism. Both verapamil and nifedipine reduce blood pressure acutely and on chronic administration. Acute administration results in reflex-activated increments of heart rate, plasma renin activity, and plasma catecholamines after nifedipine, whereas these effects are less conspicuous after verapamil. Acute diuretic, natriuretic, and uricosuric effects can be demonstrated. On repeated administration of nifedipine, a degree of tolerance develops and on long-term administration it may be necessary to combine it with a beta-adrenoceptor blocker and a diuretic. In animal experiments, calcium blockers have shown favorable effects on hypertensive cardiovascular structural changes, but such unique beneficial effects remain to be demonstrated in the human disease.