Effect of Baroreceptor Denervation on the Inhibition of Renin Release by Vasopressin*

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Abstract
Previous studies have suggested that the inhibition of renin secretion by acute administration of vasopressin in conscious dogs results from a reflex reduction in renal nerve activity. In the present investigation, this hypothesis was tested by studying the effect of total baroreceptor denervation or selective low pressure baroreceptor denervation on the suppression of PRA by vasopressin in conscious, chronically prepared dogs. In eight sham-operated dogs, a 45-min infusion of vasopressin (2.0 ng/kg .times. min, iv) decreased PRA from 10.5 .+-. 1.9 to 5.9 .+-. 1.0 ng/ml .times. 3 h (p < 0.01). Mean arterial pressure did not change (110 .+-. 10 to 107 .+-. 7 mm Hg), but heart rate decreased from 84 .+-. 9 to 69 .+-. 8 beats/min (P < 0.05). In contrast, vasopressin infusion failed to significantly decrease PRA in seven sinoaortic/cardiac denervated dogs (9.5 .+-. 1.7 to 7.4 .+-. 2.0 ng/ml .times. 3 h), although decreases did occur in three of the dogs. Mean arterial pressure increased from 104 .+-. 5 to 125 .+-. 6 mm Hg (P < 0.01), but heart rate did not change (112 .+-. 4 to 107 .+-. 5 beats/min). When renal perfusion pressure was maintained at the preinfusion level in three sinoaortic/cardiac denervated dogs, vasopressin infusion failed to decrease PRA (2.3 .+-. 0.6 to 2.4 .+-. 0.6 ng/ml .times. 3 h). In six cardiac denervated dogs, vasopressin infusion decreased PRA from 5.3 to 0.9 to 3.1 .+-. 0.7 ng/ml .times. 3 h (P < 0.01). Results obtained with two lower doses of vasopressin (0.5 and 1.0 ng/kg .times. min) were generally similar to the responses observed during infusion at 2.0 ng/kg .times. min. Angiotensin II (5.0 ng/kg .times. min) suppressed PRA in all groups of dogs. These experiments demonstrate that the inhibition of renin secretion by acute administration of vasopressin in conscious dogs is prevented by total baroreceptor denervation, but not by denervation of the low pressure baroreceptors alone. These results suggest that the suppression of renin release by vasopressin is a reflex response resulting from activation of the high pressure baroreceptors.