AJP - Regulatory, Integrative and Comparative Physiology, Vol 233, Issue 1 37-R43, Copyright © 1977 by American Physiological Society
Renin-angiotensin-aldosterone system of the normothermic marmot
P. R. Kastner, M. L. Zatzman, F. E. South and J. A. Johnson
Adrenal steroid secretion rates and the renin-angiotensin-aldosterone (RAA)
system were studied in the normothermic marmot. Adrenal secretion by the
anesthetized, laparotomized marmot was (mean +/- SEM); aldosterone 1.2 +/-
0.3 ng/min, deoxycorticosterone 16.7 +/- 11.5 ng/min, corticosterone 15.2
+/- 7.8 ng/min, and cortisol 554 +/- 108 ng/min. Four forcings were
investigated that affect feedback control at different sites:
adrenocorticotropic hormone (ACTH) and angiotensin II (AII) infusion,
sodium (Na) depletion, and Na loading. Plasma aldosterone, cortisol, Na,
and potassium (K) concentrations as well as plasma renin activity (PRA)
hematocrit (Hct), and in some studies, blood pressure were measured. ACTH
infusion increased the plasma concentrations of aldosterone and cortisol.
AII infusion increased aldosterone concentration, blood pressure, and Hct.
Na depletion increased aldosterone, Hct, and PRA; plasma Na and K were
decreased. Aldosterone concentration, Hct, and PRA decreased after salt
loading. Normothermic, salt-depleted marmots demonstrated a pronounced fall
in blood pressure following infusion of the AII analog,
1-sarcosine-8-alanine AII. The average plasma values for aldosterone, PRA,
and cortisol found in 44 control animals were: aldosterone 3.8 +/- 0.3
ng/100 ml, PRA 1.9 +/- 0.2 ng AI-ml-1-h-1, and cortisol 54 +/- 4 ng/ml. It
was concluded that normothermic marmots have a RAA system comparable to
other mammalian species.
