Experimental Renal Hypertension in Dogs FORELIMB HEMODYNAMICS

Abstract

Blood flow arid segmental intravascular pressures were measured in the pump-perfused forelimb vascular beds of 25 dogs with chronic perinephritic hypertension and 26 normotensive control dogs (either unilaterally nephrectomized or sham-operated) under pentobarbital anesthesia. Measurements were made under resting conditions (pump-perfusion pressure set equal to aortic pressure) and during response to: (1) stepwise changes in pump blood flow over the range 21-330 ml/min; (2) intrabrachial arterial injection of supramaximal doses of methacholine chloride; and (3) limb denervation. Total limb vascular resistance and segmental pressure gradients were calculated. In hypertensive dogs, as compared to normotensive dogs, resting blood flow was equal ( P >0.3) and resting limb total vascular resistance was increased ( P <0.005). Small vessel pressure gradient was increased ( P <.005) and venous pressure gradient was decreased ( P <0.005). Limb vascular resistance following methacholine injections and residual resistance following neurectomy were lower ( P <0.05) in normotensive than in hypertensive dogs. The development of hypertension was accompanied by the upward displacement of limb flow-resistance curves without discernible change in shape of the curves. These data suggest that in chronic renal hypertension in dogs: (1) the limb vascular bed participates in the increased peripheral vascular resistance; (2) the increase in limb vascular resistance is confined to the small vessel segment with no evidence found for limb venoconstriction; (3) a portion of the elevated limb vascular resistance is not attributable to neural stimuli; and (4) structural changes in vessels may account for part of the increase in limb resistance.