Conditions for stimulation of renin release by cyclic AMP in anaesthetized dogs

Abstract

Cyclic AMP (CAMP) is the intracellular mediator of β-adrenergic stimulation in most tissues. Stimulation of β-adrenoceptors increases renin release much more at low than at control arterial perfusion pressure. If β-adrenergic stimulation is mediated by cAMP, this nucleotide should also potentiate renin release at low perfusion pressure. In anaesthetized, propranolol treated dogs, the dibutyryl derivative of cAMP (DB-cAMP), which penetrates cell membranes more readily than cAMP, increased renin release significantly during renal arterial constriction at a perfusion pressure below the range of autoregulation, but no significant effect was observed at control blood pressure. A dose-response relationship could be demonstrated in propranolol treated dogs by administering DB-cAMP at 10, 100 and 1000 μg/min at low but not at control blood pressure. Since sodium excretion increased, stimulation of a macula densa mechanism is unlikely, whereas arteriolar dilation, caused by autoregulation at low blood pressure, may condition the juxtaglomerular apparatus for renin release. Infusion of cAMP had no effect on renin release either at control or low blood pressure, whereas 5′AMP exerted a marked inhibitory effect at low blood pressure. We conclude that infusion of DB-cAMP rather than cAMP stimulates renin release at low but not at control blood pressure and that this effect is not mediated by β-adrenergic receptors; cAMP may be an intracellular mediator of renin release.

Key Words:

• afferent arterioles
• 5′AMP; camp
• DB-cAMP
• renal autoregulation