Angiotensin II, vasopressin, and sympathetic activity in conscious rats with endotoxemia
Schaller, M.D.; Waeber, B.; Nussberger, J.; Brunner, H.R.
American Journal of Physiology 249(6 Pt 2): H1086-H1092
1985
ISSN/ISBN: 0002-9513 PMID: 3907375 Document Number: 252485
The role of the sympathetic nervous system, angiotensin II (ANG II), and arginine vasopressin (AVP) in maintaining blood pressure (BP) during endotoxic shock was investigated in 117 conscious male Wistar rats. After intravenous injection of 2 mg Escherichia coli endotoxin, mean BP fell within 5 min by approximately 50 mmHg and rose again to approach base-line levels within 90 min. At that time, plasma renin activity, plasma norepinephrine (NE), and vasopressin levels of the endotoxin-treated animals were, respectively, 12-, 10-, and 54-fold (P < 0.001) higher than those of the controls. The BP effect of either prazosin (0.125 mg iv), captopril (2.5 mg iv), or d(CH2)5Tyr(Me)AVP (5 .mu.g iv), a specific antagonist of the vascular effect of AVP, was evaluated over a 30-min observation period starting 90 min after administration of endotoxin or its vehicle. Captopril reduced mean BP from 116 .+-. 1.8 to a low of 109 .+-. 2.1 (SE) mmHg (P < 0.05, n = 8) only in rats pretreated with endotoxin, whereas the vasopressin antagonist had no depressor effect even during endotoxemia. The BP drop induced by prazosin in rats exposed to endotoxin (-21 .+-. 3.3 mmHg, n = 6) did not significantly differ from that observed in control rats (-14 .+-. 3.4 mmHg, n = 6). A dose-response curve to NE, ANG II, and lysine vasopressin was also performed. In endotoxin-treated rats the mean BP response to all agonists was markedly suppressed (P < 0.001). It appears therefore that recovery of BP following endotoxin-hypotension occurs in the face of extremely high plasma levels of NE, ANG II, and vasopressin. Nevertheless probably due to the observed decrease in vascular responsiveness, the contribution of the three vasopressor systems to BP maintenance is hardly enhanced during endotoxemia.