AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 2 365-R369, Copyright © 1989 by American Physiological Society
Effects of converting-enzyme inhibitor on hemodynamic actions of ANP in renal hypertensive rats
M. G. Salom, F. J. Fenoy, A. C. Ingles, L. Martinez and T. Quesada
Departamento de Fisiologia, Facultad de Medicina, Murcia, Spain.
In the present study, we have evaluated whether the hemodynamic effects of
atrial natriuretic peptide (ANP) infusion in two-kidney, one-clip (2K, 1C)
hypertensive rats are mediated by inhibition of the renin-angiotensin
system (RAS). Hemodynamic determinations were performed by thermodilution
in conscious, chronically instrumented animals. ANP (1.5
micrograms.kg-1.min-1) and converting-enzyme (CE) inhibitor captopril (1
mg/kg plus 1 mg.kg-1.h-1), produced a similar fall of blood pressure
through different hemodynamic mechanisms. ANP induced hypotension by
decreasing cardiac index (CI; from 337.3 +/- 24.9 to 255.1 +/- 21.3
ml.min-1.kg-1, P less than 0.001), whereas a fall in total peripheral
resistance (TPR) was observed during CE inhibition (from 0.568 +/- 0.02 to
0.488 +/- 0.02 mmHg.min.ml-1.kg, P less than 0.05). In addition, the
ANP-induced decrease in CI was not significantly modified by previous CE
inhibition. Furthermore, the decrease in TPR induced by CE inhibition did
not change when CE inhibitor was administered during ANP treatment. The
results of the present study indicate that the acute hemodynamic responses
to ANP in 2K, 1C hypertensive rats are not mediated through antagonism of
the vasoconstrictor actions of the RAS.
