AJP - Heart and Circulatory Physiology, Vol 246, Issue 4 573-H578, Copyright © 1984 by American Physiological Society
Alpha 1-adrenoceptor blockade in renal hypertensive rats with low and high renin levels
B. Waeber, J. Nussberger and H. R. Brunner
A total of 75 male Wistar rats with one-kidney, one-clip renal hypertension
was maintained on either a regular (RNa) or a low-salt (LNa) diet for 3 wk
after clipping. Blood pressure in the unanesthetized rats was equally
elevated independent of sodium intake. Plasma renin activity was higher in
LNa animals, and blood pressure was renin dependent only in this group, as
evidenced by the blood pressure response to 10 mg/kg captopril iv. There
was no significant difference in plasma catecholamines between RNa and LNa
rats, although in the former the sympathetic nervous system is believed to
play a major role in sustaining high blood pressure. The acute intravenous
administration of 0.5 mg/kg prazosin did not induce a more pronounced blood
pressure fall in the RNa rats. Prazosin enhanced plasma norepinephrine
levels similarly in both groups, but epinephrine levels only rose in the
LNa animals. Prazosin also markedly stimulated plasma renin activity
rendering blood pressure renin dependent even in RNa rats. Thus, using
alpha 1-adrenoceptor blockade, it has not been possible to demonstrate that
the blood pressure elevation of salt-repleted one-kidney, one-clip renal
hypertensive rats is due to an enhanced sympathetic nerve activity. Data
obtained with sympatholytic agents must be interpreted with great caution
if renin activity cannot be kept unchanged.
