Renin-angiotensin-aldosterone system of the hibernating marmot [Le système rénine-angiotensine-aldostérone de la marmotte hibernante].

Résumé

The concentrations of several plasma constituents were measured at different times thoughout a bout of hibernation. Between the lst day of hibernation and the 9th day, plasma aldosterone increased from a level one-half of that found in normotnermic animals to within the normothermic level; plasma renin activity (PRA) demonstrated the same pattern as aldosterone, but initial (PRA) wag within the normothermic range and increased about twofold. Plasma cortisol decreased from the lst to the 6th or 7th day of hibernation. PIasma sodium and potassium increased gradually throughout the course of hibernation, while hematocrit and blood urea nitrogen were unchanged. PIasma glucose increased until midcycle and then decreased toward the level found at day 1. AIthough marmots that had hibernated for 2 days demonstrated an increase in blood pressure following synthetic angiotensin II (AII) infusion, the AII analog (l-sar-8-ala-angiotensin II) had no effect on the blood pressure of marmots at this point in a bout of hibernation. lt was concluded that the rising level of aldosterone found during a bout of hibernation was a consequence of enhanced stimulation of a depressed adrenal cortex by increased PRA and increased plasma potassium concentration. Enhanced renin secretion, in turn, was assumed to be initiated by reduced renal afferent arteriolar pressure and a, diminished, load of sodium to the distal tubule (macula densa) secondary to, decreased blood pressure. Plasma aldosterone is therefore sufficiently high to prevent large renal losses of Na during arousal from hibernation.