[Role of alpha 1 adrenergic receptors in water balance in the rat]

The effects of phenylephrine (alpha 1 +) and prazosin (alpha 1 -) on water intake, diuresis, food intake and blood pressure were compared in conscious normal and diabetic insipidus (DI) Long Evans rats. The two drugs did not change the values measured on 24 hours in the two groups of animals (tables I and II). Phenylephrine induced a diuretic response in both normal and DI rats during the two first hours. Water intake was decreased in normal rats and increased in DI animals (fig. 1). Prazosin induced an antidiuretic effect in the two groups of animals, an increase in water intake in normal rats and a decrease in water intake in DI animals (fig. 2). Blood pressure was not changed in the two groups of animals two hours after injection. The comparison between the different results shows that the first changes induced by phenylephrine or prazosin were changes in diuresis. Since the two drugs act in a same way on the diuresis of normal and vasopressin--deprived rats, it is concluded that the neurohypophysial peptide is not involved in the variations of urinary volume induced by the alpha 1-adrenergic drugs.

The effect of flurbiprofen on the responses to frusemide in healthy volunteers

Ten subjects participated in a four-way, open, crossover study to investigate the effect of frusemide, flurbiprofen, flurbiprofen plus frusemide, and placebo on urinary volume, sodium, and potassium. Compared with placebo, flurbiprofen was shown to significantly reduce all three parameters. The diuretic effect of frusemide was reduced by the addition of flurbiprofen but not to a statistically significant degree. The reduction was less than in previous reports using indomethacin. As flurbiprofen is a more potent inhibitor of prostaglandin synthesis than indomethacin, these data cast doubt on the theory that nonsteroidal anti-inflammatory drugs antagonize the action of diuretics by prostaglandin synthetase inhibition. The methods for assaying the two drugs are described. A pharmacokinetic explanation of the reduction of the diuretic effects of frusemide by flurbiprofen was sought but not found.

Influence of a prostaglandin inhibitor and a mineralocorticoid on the antidiuretic and hormonal response to an osmolar load

To examine the influence of prostaglandins (PGs) and sodium-volume status on the urinary excretion and action of arginine-vasopressin (AVP), we studied the response to a hypertonic saline infusion (2.5% NaCl, 0.06 ml/kg/min for 3 h) in 8 healthy males under three different conditions: 1) on an ad libitum salt diet (C), 2) after 4-day treatment with indomethacin (IDM) 150 mg/d, 3) after 4-day treatment with fluorohydrocortisone (9 alpha FF) 0.6 mg/d. The rise of urine osmolality and the decrease of free water clearance were identical in all three studies. Basal urinary PGE2, PGF2 alpha and AVP were decreased during IDM and unchanged during 9 alpha FF, compared to C. The increment of urinary AVP was similar during C and IDM but significantly greater with 9 alpha FF (P less than 0.02) although urinary PGs were higher at the end of the infusion. In conclusion, despite markedly different hormonal patterns and sodium status in the three protocols, the antidiuretic response to an osmolar load is preserved suggesting an adaptive mechanism maintaining a constant balance between AVP and PGs.

Preclinical studies of indapamide, a new 2-methylindoline antihypertensive diuretic

Indapamide is a new indoline antihypertensive diuretic agent whose chemical structure differs substantially from those of the thiazides. The hydrophobic indoline moiety of indapamide confers a lipid solubility to the molecule that is 5 to 80 times greater than that of the thiazide diuretics. Thus indapamide accumulates in vascular smooth muscle at a concentration 10 times higher than that of protein-free perfusate. The affinity of indapamide for vascular smooth muscle manifests itself in vitro and in vivo as a decrease in reactivity following various pharmacologic interventions. Moreover, in vitro studies have demonstrated that indapamide decreases the inward calcium current and the transmembrane influx of calcium. The diuretic effect of indapamide is predominantly due to inhibition of sodium reabsorption at the cortical diluting segment of the distal convoluted tubule. In animal studies, intravenous indapamide has no effect on glomerular filtration rate or renal blood flow. Indapamide is well absorbed and extensively metabolized in animals and humans, with biliary excretion being the predominant route of elimination in animals. Most important, repeat administration of indapamide to dogs with both kidneys removed produces no accumulation of intact indapamide or its metabolites. Extensive drug safety studies in animals indicate that indapamide produces no overt toxicity and exhibits a good margin of safety.

[Nephrotoxicity of contrast media for urography in patients with chronic renal insufficiency]

The incidence of nephrotoxicity caused by intravenous pielography (IVP) contrast media was retrospectively evaluated in 42 patients with chronic renal failure. In 14 patients renal function was acutely impaired after IVP. In most cases the dysfunction was only temporary; in 3 cases permanent damage was induced, one of which required dialytic treatment. In the cases described there appears to be no correlation between the degree of renal failure and the incidence of nephrotoxicity but the former is clearly linked to the severity of the nephrotoxic response.

Effect of aprotinin on the renal response to vasopressin in diabetes insipidus rats

The renal response to arginine vasopressin was investigated with and without the simultaneous administration of the kallikrein inhibitor, aprotinin, in conscious Brattleboro homozygous rats with hereditary diabetes insipidus. Arginine vasopressin caused a marked antidiuretic response (urinary osmolality increased from 118 to 739 mosmol/l) which was accompanied by a significant increase in urinary prostaglandin excretion (prostaglandin E2 and F2 alpha excretion increased by 182 and 441%, respectively). Kallikrein excretion remained unchanged after arginine vasopressin infusion. The infusion of aprotinin diminished urinary kallikrein activity to undetectable levels, decreased potassium excretion significantly and caused a slight fall in urinary prostaglandin excretion. However, aprotinin failed to modify the arginine vasopressin-induced enhancement in prostaglandin excretion (prostaglandin E2 and F2 alpha excretion increased by 168 and 442%, respectively), and the antidiuretic response was also similar to that observed under control conditions. These results indicate that the kallikrein-kinin system is not involved in the renal response to vasopressin in the Brattleboro rat.

Treatment of cerebral infarction with dimethyl sulfoxide in the mongolian gerbil

Dimethyl sulfoxide (DMSO) has been reported to have beneficial effects in the treatment of central nervous system trauma, possibly due to its reported anti-inflammatory, antiedemic, anticoagulate, diuretic, hypothermic, vasodilatory, and respiratory stimulatory effects as well as an ability to correct membrane instability and penetrate the blood-brain barrier. In this paper we discussed these properties, and how they may be of benefit in ischemic cerebral infarction and elevated intracranial pressure. We also described a study we performed to determine if treatment with DMSO would decrease the morbidity and mortality from experimental cerebral infarction.

[Pharmacologic treatment of patent ductus arteriosus in premature infants]

Sixty-one preterm infants (birthweight, 1.529 +/- 450g; gestational age, 31,9 +/- 2,4 weeks) developed a large DAP. Seventy-eight per cent required mechanical ventilation and 75,5% had hyaline membrane disease. Pharmacological closure of the DAP with oral indomethacin was attempted on 31. A steady improvement was achieved in 64,5%. The postnatal age of responders was lower than that of non-responders. Neonatal survival was over 90% but long-term survival dropped to 64,5% linked to a high incidence of bronchopulmonary dysplasia. The patients with bronchopulmonary dysplasia had received indomethacin later than the others. It was found that postnatal age at the time of indomethacin administration correlated with the days of mechanical ventilation later required by the survivors.

Dopamine versus dobutamine after open-heart surgery

The haemodynamic effects of dopamine and dobutamine were compared in a cross-over study of 12 patients in the early postoperative phase after open-heart surgery. The drug infusion rates (dopamine (microgram/kg/min) mean 6.5, range 2.8-12, dobutamine (microgram/kg/min) mean 7.9, range 4.3-12.3) were adjusted so that the cardiac output increased by 50%. With both drugs this was achieved through simultaneous increases in stroke volume (dopamine + 16%, dobutamine + 9%) and heart rate (dopamine + 31%, dobutamine + 38%). The systemic vascular resistance did not change with dopamine but decreased significantly (-18%) with dobutamine. Therefore, the systolic and diastolic arterial blood pressures rose significantly more with dopamine than with dobutamine. The left atrial pressure increased with dopamine but was unchanged with dobutamine. The urine output was significantly higher with dopamine than with dobutamine.

Sodium balance and antidiuresis in thiazide-treated rats with diabetes insipidus

A sodium deficit was induced in Brattleboro rats by lowering the dietary sodium content. Urine volume was only slightly reduced. Addition of hydrochlorothiazide to the food caused a small, transient sodium deficit but led to a marked, sustained antidiuresis. The acute administration of a large dose of hydrochlorothiazide produced a larger, sustained sodium deficit but no lasting antidiuresis. These results indicate that sodium depletion cannot account for the antidiuresis of hydrochlorothiazide treatment in diabetes insipidus.

[Mechanism of the diuretic action of parathormone]

The effect of parathyroidin, calcium chloride and parathyroidin combined with verapamil (blocking the inclusion of calcium ions into cells) on diuresis and electrolyte excretion with the urine was studied in experiments on dogs. It was shown that after a single intravenous injection of parathyroidin in a dose of 2 U/kg body weight diuresis and natriuresis twice augmented and potassium excretion increased 1.6 times one hour following the drug injection. The intravenous injection of 10% calcium chloride solution or parathyroidin combined with verapamil did not produce such an effect. The mechanism of parathyroid hormone diuretic action is likely to be due to intensified calcium ion inclusion into the renal tubular cells.

An investigation of the importance of the adrenal gland to the action of dopamine in the rat kidney

1 In the rat, administration of dopamine is associated with diuresis, natriuresis and a decreased excretion of K+. The site of action of dopamine in mediating these responses has been investigated. 2 Urine volume, and urinary Na+, K+, Cl- and dopamine concentrations have been measured in adrenalectomized and sham-operated male Wist ar rats. 3 As expected, adrenalectomy decreased urine volume and increased Na+ and Cl- excretion; at the same time the amount of dopamine excreted fell, and K+ excretion did not change. 4 Administration of either 3% NaCl (20 ml/kg orally) or frusemide (100 mg/kg s.c.) significantly elevated dopamine excretion after adrenalectomy. 5 When dopamine, 1, 10 and 30 mg/kg (s.c.) was given to adrenalectomized rats, the diuresis and fall in K+ excretion seen in control animals was still present. No further natriuresis, over and above the already high urinary Na+ levels, was observed. 6 The results show that the three actions of dopamine in inducing diuresis and natriuresis, and decreasing K+ excretion, are clearly separable. 7 It is further argued that in mediating these effects the main site of action of dopamine is the kidney rather than the adrenal gland.

The diuretic action of noradrenaline and dopamine in rats with chemical serotoninectomy and central nervous system sympathectomy

It was demonstrated that dopamine administered into the lateral ventricle of rats with chemically induced sympathectomy of the central nervous system had an evident diuretic effect observed 4 as well as 24 hours after its injection. Noradrenaline, on the other hand, increased diuresis in control rats and in those with chemical serotoninectomy, but only in the first 4 hours of the experiment. Chemical sympathectomy of the central nervous system abolished the diuretic effect of noradrenaline. The results of the experiment confirm the role of mainly dopaminergic receptors in the central regulation of diuresis in this experimental model.

Randomized comparative study of efficacy of furosemide versus spironolactone in nonazotemic cirrhosis with ascites. Relationship between the diuretic response and the activity of the renin-aldosterone system

Loop and distal diuretics are the basic drugs for the treatment of ascites. Although pharmacologic studies indicate that the natriuretic potency of loop diuretics is much greater than that of distal diuretics, there are no studies comparing the efficacy of these drugs in cirrhosis. Forty nonazotemic cirrhotic patients with ascites and avid sodium retention were randomly allocated into two groups. Group 1 contained 21 patients treated with furosemide; group 2 contained 19 patients treated with spironolactone. The initial doses were 80 and 150 mg/day, respectively. These doses were increased to 160 and 300 mg/day, respectively, if there was no response. Cases not responding to furosemide and spironolactone were later treated with spironolactone and furosemide, respectively. In group 1, 11 of the 21 patients responded to furosemide, while in group 2, 18 of the 19 patients responded to spironolactone (p less than 0.01). Of the 10 patients in group 1 not responding to furosemide, 9 responded later to spironolactone. The diuretic response to furosemide and spironolactone was related to the activity of the renin-aldosterone system. Patients with higher renin and aldosterone did not respond to furosemide and required 300 mg/day of spironolactone to achieve a diuretic response. These results indicate that (a) at the dosages used in the study, spironolactone is more effective than furosemide in nonazotemic cirrhosis with ascites, and (b) the activity of the renin-aldosterone system influences the diuretic response to furosemide and spironolactone in these patients.

Urinary excretion of renin in the dog: effect of changes in plasma renin

By using standard clearance and stop flow techniques, studies were carried out in anesthetized dogs to clarify further the mechanism(s) of excretion of renin in urine. The clearance of renin was 0.61 +/- 0.19 ml/min in control experiments and increased significantly to 1.26 +/- 0.38 ml/min after furosemide. The fractional excretion of renin increased from 1.51 +/- 0.45% during control to 3.90 +/- 0.98% after furosemide. The rate of excretion of renin was increased 10-fold during furosemide diuresis associated with a 10-fold increase in plasma renin concentration. Extracellular fluid volume expansion also produced a diuresis but no increase in plasma renin or renin excretion. Hemorrhage produced a 3.5-fold increase in plasma renin concentration and a 200-fold increase in urinary excretion of renin. When renal artery perfusion pressure was reduced to one kidney, the excretion of renin in the urine from that kidney increased, whereas there was no significant change in the excretion from the contralateral kidney. Reduction in renal artery perfusion pressure was associated with a 3-fold increase in the concentration of renin in the renal vein from the experimental kidney but an insignificant 2-fold increase in the arterial plasma renin concentration. Stop-flow studies demonstrated that renin enters the urine with the glomerular filtrate. The decreased concentration of renin in samples from the proximal tubule suggests that renin is being metabolized and/or reabsorbed in this nephron segment. In the distal nephron, there appears to be a site in which renin may be added to the tubular fluid. The results of these studies suggest that renin excretion in the urine is a complicated process. Excretion of renin in the urine is related in part to plasma renin activity but probably more importantly to the rate of production of renin in the kidney.

[Low renin variant of hypertension: functional relations of the renin-aldosterone pressor system]

Renin-aldosterone function was studied in 23 patients with low-renin essential hypertension (LREH) under resting and stimulated conditions. Patients were selected on the basis of differential diagnostic tests of renin-angiotensin stimulation and inhibition as well as roentgeno-radiologic findings in order to rule out adrenal lesions. The results were compared with those of patients with primary aldosteronism and with essential hypertension where renin activity can be stimulated under similar sodium balance conditions. Intravenous or prolonged furosemide administration was shown to be the test of choice for the diagnosis of renin suppression. The renin-aldosterone system of LREH patients featured subnormal renin activity and normal aldosterone levels in baseline conditions, and the lack of renin stimulation together with limited aldosterone stimulation following functional tests. The analysis of changes in diuresis, natriuresis and the pattern of Na/K coefficient points to a great diuretic and natriuretic effect of furosemide in patients with LREH.