AJP - Heart and Circulatory Physiology, Vol 246, Issue 1 25-H30, Copyright © 1984 by American Physiological Society
Role of angiotensin II, alpha-adrenergic system, and arginine vasopressin on arterial pressure in rat
M. S. Paller and S. L. Linas
Three pressor systems regulate arterial pressure (MAP): angiotensin II (ANG
II), the alpha-adrenergic system, and arginine vasopressin (AVP). In this
study we determined the ability of each system to support MAP in the
conscious rat when the other two systems were inactivated. After
administration of the converting-enzyme inhibitor teprotide (CEI) and the
alpha-adrenergic receptor antagonist phenoxybenzamine (POB), MAP decreased
40% as a result of a 45% decrease in peripheral vascular resistance (PVR).
Despite hypotension, plasma AVP levels were not increased, and an AVP
pressor antagonist (AVP-A) did not result in a further decrease in MAP.
Thus the profound hypotension after POB plus CEI was the result of
inhibition of all three systems. POB, rather than CEI, prevented AVP
release since following hypotensive hemorrhage, plasma levels reached 51
+/- 13 pg/ml with CEI but only 4.7 +/- 0.8 pg/ml with POB. To study the
pressor effect of AVP alone, AVP was infused in POB plus CEI-treated rats.
AVP increased MAP (from 68 +/- 4 to 92 +/- 5 mmHg; P less than 0.005) and
plasma AVP (to 13.8 +/- 1.9 pg/ml). Since POB inhibited both the AVP and
the alpha-adrenergic system, the role of ANG II alone was determined in
POB-treated rats. In the presence of ANG II MAP was 97 +/- 1 mmHg. To study
the alpha-adrenergic system, MAP was determined in CEI plus AVP-A-treated
rats. In the presence of an intact alpha-adrenergic system MAP was 101 +/-
1 mmHg. We conclude that PVR and MAP are profoundly decreased in the
absence of all three pressor systems.(ABSTRACT TRUNCATED AT 250 WORDS)
