Cerebral osmoregulatory reduction of plasma renin concentration in sheep

A centrally mediated inhibitory influence of plasma hypertonicity on renin secretion was investigated in conscious, Na-depleted sheep. Infusions of hypertonic solutions were made into the carotid artery or jugular vein, and the effects on plasma renin concentration (PRC) compared. Intracarotid infusion of 1.65 M NaCl significantly reduced PRC (to 74% of the pre-infusion value) within 15 min of the commencement of the infusion whereas corresponding intrajugular infusion did not. Intracarotid infusion of 3 M sorbitol for 45 min also reduced PRC (to 64% of the pre-infusion level) significantly after 15 min of infusion. By contrast, neither intrajugular infusion of 3 M sorbitol, nor intracarotid infusion of isotonic 0.15 M NaCl for 45 min significantly reduced PRC. Intracarotid infusion of hypertonic sorbitol for 45 min did not inhibit PRC in sheep with cerebral lesions of the lamina terminalis. These results show that plasma hypertonicity may have an inhibitory influence on renin secretion. The inhibition is probably mediated by an effect of hypertonicity on the CNS, rather than a direct effect on the kidney.