AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 4 912-R917, Copyright © 1990 by American Physiological Society
Regional hemodynamic effects of endothelin-2 and sarafotoxin-S6b in conscious rats
S. M. Gardiner, A. M. Compton and T. Bennett
Department of Physiology and Pharmacology, Medical School, Queen's Medical Centre, Nottingham, United Kingdom.
Regional hemodynamic responses to bolus doses (4 and 40 pmol) and 60-min
infusions (12 and 120 pmol/h) of endothelin-2 (ET-2) and sarafotoxin-S6b
(S6b) were measured in conscious Long-Evans and Brattleboro rats
chronically instrumented with pulsed Doppler flow probes. In both strains
of rat the two bolus doses of ET-2 and S6b peptides caused an initial fall
in mean blood pressure (MBP). At the higher dose S6b caused a greater fall
in MBP than ET-2. In Long-Evans rats the fall in MBP after S6b was
associated with renal, mesenteric, and hindquarters vasodilatations; in
Brattleboro rats there was no renal or mesenteric vasodilatation with S6b.
The high dose of ET-2 caused early mesenteric vasoconstriction in both
strains. After the initial fall in MBP there were dose-dependent increases
in MBP together with renal and mesenteric vasoconstrictions. These effects
were generally greater after S6b than after ET-2 and no less marked in
Brattleboro than in Long-Evans rats, indicating that release of endogenous
vasopressin was not an indispensable component of the response. Infusions
of the higher dose of ET-2 or S6b caused increases in MBP only, associated
with renal, mesenteric, and hindquarters vasoconstrictions. The results
indicate that S6b is a more potent stimulus than ET-2 of vasodilator
mechanisms in vivo; despite this, S6b also exerts more marked
vasoconstrictor effects than ET-2.
