Role of renal sympathetic nerves in renin inhibition by elevated left atrial pressure.

We have reported that the renin response to systemic hypotension during a simultaneous increase in left atrial pressure (LAP) depends, in part, on intact renal nerves. Because efferent neural control of renin release is mediated by renal sympathetic nerves, we tested the hypothesis that withdrawal of renal sympathetic tone is an essential component of the inhibitory mechanism. In conscious dogs, the ascending aorta was partially constricted to produce a simultaneous decrease, of up to 30%, in renal perfusion pressure (RPP) and a rise in LAP. Sympathetic neural control of renin release was reversibly blocked with propranolol. Propranolol infusion did not affect the increases in LAP or atrial natriuretic factor (ANF) during ascending aortic constriction. There was no increase in renin (P greater than 0.1) during ascending aortic constriction, with or without propranolol infusion. Identical reductions in RPP during constriction of the abdominal aorta caused renin to rise (P less than 0.03). Therefore acute withdrawal of renal sympathetic tone is not necessary for the inhibition of the renin response to systemic hypotension by elevated LAP.