Role of neural pathways in renin response to intravascular volume expansion

This study was designed to evaluate the physiological importance of cardiopulmonary receptors with vagal afferents in controlling renin release during perturbations in blood volume. Intravascular volume of chloralose-anesthetized dogs was expanded by 7.5 ml/kg body wt, with an isotonic isoncotic solution containing 3% dextran for colloid. Volume expansion resulted in a 50% decline in renin secretion. However, volume expansion after bilateral cervical vagotomy, the proposed afferent limb of the reflex, also suppressed renin release. In another group of animals, the left kidney was surgically denervated and the right kidney extirpated, and again infusion suppressed resin release. In all groups, the infusion significantly suppressed renin release when compared to each dog's own control period, as well as when compared to the corresponding time controls. Our data indicate that the renin response to intravascular volume expansion was not mediated solely by the vagi or renal nerves. A combination of intrarenal factors may, however, have been responsible for the suppression of renin release observed. Our results do not support the hypothesis that the renin-angiotensin system is an efferent limb of the cardiopulmonary reflex during adjustments to alterations in blood volume.