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Resting cardiovascular status and vasodilator function in a vasopressin-deficient, hypertensive strain of rat
S M Gardiner1, J E March, P A Kemp
1Department of Physiology and Pharmacology, University of Nottingham Medical School, Queen's Medical Centre, UK.
Objective:
To assess resting haemodynamic status and vasodilator responses in normotensive vasopressin-deficient (DI/N) and hypertensive vasopressin-deficient (DI/H) rats.
Design And Methods:
DI/N and DI/H rats were chronically instrumented with pulsed Doppler probes and intravascular catheters and were given 3-min infusions of acetylcholine (56 nmol/kg per min), bradykinin (36 nmol/kg per min) or salbutamol (2.1 nmol/kg per min) in the absence and presence of the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME; 183 nmol/kg per min) or vasopressin (5 pmol/kg per min), to control for the pressor effects of L-NAME.
Results:
The DI/H rats had a higher mean arterial blood pressure, lower hindquarters flow and lower vascular conductance than the DI/N rats. In the two strains of rat the haemodynamic responses to L-NAME, as well as to acetylcholine, bradykinin and salbutamol, in the absence or presence of L-NAME, were similar. In both strains of rat the acetylcholine-induced renal vasodilation was blocked by L-NAME, but bradykinin-induced mesenteric and salbutamol-induced hindquarters vasodilation involved L-NAME-sensitive and L-NAME-insensitive components.
Conclusions:
There is vasoconstriction in the hindquarters but not in renal and mesenteric vascular beds of DI/H rats. Vasodilator function is not necessarily impaired in congenital hypertension.