Influence of Adrenergic Nervous System on Vasodilator-Induced Renin Release in the Conscious Rat

The influence of the adrenergic nervous system on vasodilator-induced renin secretion was studied in conscious rats with chronically implanted jugular and carotid cannulae. Hydralazine (0.1, 0.5, and 1 mg/kg body wt) was administered iv to rats and the dose-response relationship to plasma renin activity was calculated using linear regression analysis. These data were compared to results obtained in the same rats when similar doses of hydralazine were administered 15 min after pretreatment with iv propranolol (1 mg/kg body wt). A highly significant dose-response relationship was demonstrated between hydralazine dose and plasma renin activity (r = 0.83; P < 0.0005). In the presence of propranolol the increase in plasma renin activity was approximately 50% of the increase noted in studies without propranolol. The dose-response relationship remained highly significant (r = 0.64; P < 0.0005) in the presence of β-adrenergic blockade, which was confirmed by the failure to increase heart rate despite a significant reduction in blood pressure. These results show that in the conscious rat renin secretion following vasodilatation is only partially controlled through the adrenergic nervous system and that other mechanisms appear to play a prominent role in this response.