RESTING CARDIOVASCULAR STATUS AND VASODILATOR FUNCTION IN A VASOPRESSIN-DEFICIENT, HYPERTENSIVE STRAIN OF RAT

Objective: To assess resting haemodynamic status and vasodilator respo nses in normotensive vasopressin-deficient (DI/N) and hypertensive vas opressin-deficient (DI/H) rats. Design and methods: DI/N and DI/H rats were chronically instrumented with pulsed Doppler probes and intravas cular catheters and were given 3-min infusions of acetylcholine (56 nm ol/kg per min), bradykinin (36 nmol/kg per min) or salbutamol (2.1 nmo l/kg per min) in the absence and presence of the nitric oxide synthase inhibitor N-G-nitro-L-arginine methyl ester (L-NAME; 183 nmol/kg per min) or vasopressin (5 pmol/kg per min), to control for the presser ef fects of L-NAME. Results: The DI/H rats had a higher mean arterial blo od pressure, lower hindquarters flow and lower vascular conductance th an 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 r at 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 compone nts. Conclusions: There is vasoconstriction in the hindquarters but no t in renal and mesenteric vascular beds of DI/H rats. Vasodilator func tion is not necessarily impaired in congenital hypertension.