Dose-dependent opposite effects of angiotensin on renal sodium excretion

Renin-angiotensin-aldosterone system in exaggerated natriuresis of chronic glomerulonephritis

Angiotensin II (AII) and aldosterone (Aldo) in plasma, blood pressure (BP) and urinary excretion of sodium were studied before, during and in two periods after intravenous sodium loading with 500 ml of sodium chloride solution (50 g/l) in 11 normotensive and 10 hypertensive patients with histologically verified chronic glomerulonephritis and creatinine clearance in the range from 11 to 167 ml/min, and in 10 normotensive control subjects. The absolute increase of sodium excretion during loading was higher in the patients grouped together and in the hypertensives alone, but not in the normotensive patients when compared with the control subjects. No correlation was found between sodium excretion and control mean BP or change in mean BP during loading. AII and Aldo were suppressed during loading in both patients and control subjects. In the patients but not in the control subjects the increase of sodium excretion correlated positively with pre-infusion value of AII and negatively with change in AII during the sodium loading. No correlation was found between sodium excretion and Aldo and changes of Aldo. In conclusion, the results might suggest that the renin-angiotensin system is involved in the regulation of exaggerated natriuresis in chronic glomerulonephritis.

Effect of angiotensin, noradrenaline, vasopressin and aldosterone on urinary kallikrein excretion in the rat

In male Wistar rats, under osmotic diuresis, the effect of angiotensin II, noradrenaline, vasopressin and aldosterone on urinary kallikrein excretion were evaluated. Angiotensin II did not modify but all the others drugs used increased significantly the urinary kallikrein excretion. In all the groups studied the urinary sodium excretion increased. No modifications were observed in urine flow, glomerular filtration rate, urine osmolality and potassium excretion. The urinary kallikrein excretion was always positively correlated with the urinary flow and urinary sodium excretion. No correlation was observed with the other parameters studied. These findings suggest that noradrenaline, vasopressin and aldosterone are important stimulators of the urinary kallikrein excretion. Probably, kallikrein is one of the mechanisms involved in the regulation of urinary sodium excretion.

Renal tubular flow dynamics during angiotensin diuresis in the rat

1. Tubular size and lissamine green transit times were measured in rat kidneys undergoing a diuretic response to angiotensin II (0.5 mug/kg per min), and compared with the changes observed during diuresis induced by osmotic diuretics, noradrenaline and chlorothiazide.2. Angiotensin always caused a marked prolongation in proximal and distal tubular transit times; individual distal convolutions were coloured for prolonged periods, and lissamine green appeared in high concentration in distal tubules.3. Marked changes were observed in superficial tubular calibre during a stable diuretic response to angiotensin. Where distal tubular diameter was normal for the rate of urine flow, proximal tubular volume was generally reduced. In a number of experiments, however, distal tubules were markedly dilated, and in these cases proximal tubular volume was also often increased. Angiotensin may therefore be capable of causing a degree of internal hydronephrosis in the rat kidney.4. Prolongation of dye transit times, and the appearance of a concentrated lissamine green bolus in distal tubules, was suggestive of a decreased superficial nephron flow rate, indicating that the diuretic effect of angiotensin may take place only through deeper nephrons.

The effect of the renin-angiotensin system on mucosal water and sodium transfer in everted sacs of rat jejunum

1. Mucosal water and sodium transfer were measured in everted sacs of rat jejunum.2. Rats maintained on a high sodium diet did not show consistently reduced mucosal water transfer and aldosterone also failed to stimulate transfer unless the control untreated values were low.3. Adrenalectomy produced little reduction in mucosal water transfer and aldosterone was without effect on water transfer in sacs from adrenalectomized rats.4. Vasopressin had no effect on mucosal transfer.5. Levels of water transfer were not reduced after hypophysectomy nor did aldosterone injection increase transfer.6. Mucosal water transfer in sacs from adrenalectomized-nephrectomized rats was low and was significantly increased by aldosterone injection or by injection of crude kidney extract.7. A significant increased mucosal water and sodium transfer was observed when sacs from adrenalectomized-nephrectomized rats were incubated with angiotensin at a concentration of 10(-10)g/ml.8. It is suggested that the renin-angiotensin system may be involved in the maintenance of sodium homoeostasis by a direct action on sodium transporting mechanisms.

Circulatory changes and renin secretion in sheep in response to feeding

1. The effect of feeding on the circulation, on renin release and on renal function has been examined in the sheep.2. There was a rapid reduction of plasma volume within 15 min of starting to eat dry feed.3. This was accompanied by an abrupt rise in systolic blood pressure and by a more gradual and prolonged elevation of heart rate.4. Within 30 min of feeding there occurred renal conservation of sodium and water which continued for at least 2-3 hr.5. Renin was released into the circulation of sheep that ate rapidly; slow feeders did not show this response.6. The rise in plasma renin concentration was inhibited by infusing a solution similar in composition to mixed saliva at a rate that prevented the change in plasma volume.7. It is concluded that the rapid transfer of sodium and water from the circulation to the rumen via the saliva during ingestion of dry feed is sufficient to activate the renin/angiotensin system.