Contribution of vasopressin and the sympathetic nervous system in the early phase of high sodium one-kidney renal hypertension.

This study assessed the contributions of the sympathetic nervous system and arginine vasopressin to the onset of one-kidney, one-wrap (1K1W) renal hypertension in rats fed a high sodium diet. Two weeks before renal wrap or sham wrap, rats were given a high sodium diet and water ad libitum. At 3 days postwrap, resting mean arterial pressure (MAP) was significantly greater in renal-wrapped rats. The contributions of the sympathetic nervous system and vasopressin to blood pressure (BP) were assessed by ganglionic blockade and vascular vasopressin receptor antagonism, respectively. Depressor responses to ganglionic blockade were significantly greater in the normotensive rats as compared to the hypertensive rats. Administration of vasopressin antagonist caused a significant fall in pressure only in wrapped rats. In addition, enhanced pressor responses to bolus injections of vasopressin were observed in hypertensive rats. These results indicate that during this phase of the hypertension there is an activation of the vasopressin pressor system without an increase in neurogenic function. Equalization of arterial pressure occurred only when both systems were blocked, regardless of the order of blockade, which indicated that the sympathetic nervous system and vasopressin interact to maintain the hypertension. Comparison of depressor responses to the blocking agents revealed that the interaction is compensatory in nature since the contributions of the sympathetic nervous system and vasopressin to the maintenance of arterial pressure were greater when the other system was blocked.