Sympathetic nervous system and renin release from submaxillary glands in vitro

We previously reported that alpha- but not beta-adrenergic agonists stimulate renin release from mouse submaxillary glands in vivo. The present studies were undertaken to determine if these in vivo effects were due to a direct action on the submaxillary glands and to find out if cyclic AMP (cAMP) might be involved in submaxillary renin release. Pooled mouse submaxillary gland slices were incubated in Krebs-Ringer bicarbonate medium following a preincubation period, and renin release was measured by a radioimmunoassay for the direct measurement of submaxillary gland renin. Tissue cAMP levels were also measured. Addition of the alpha-adrenergic agonists, phenylephrine or norepinephrine, significantly increased renin release (P less than 0.01 vs. control) while decreasing tissue cAMP levels (P less than 0.01 vs. control). In contrast, addition of the beta-adrenergic agonist isoproterenol markedly increased cAMP levels (P less than 0.01 vs. control) and decreased renin release (P less than 0.05 vs. control). Pretreatment of the slices with the alpha-blocker phenoxy genzamine inhibited the effect of phenylephrine. These results indicate that alpha-adrenergic agonists cause renin release from submaxillary glands which is accompanied by a fall in tissue cAMP levels. This is in contrast to renin release from the kidney which is stimulated by beta-adrenergic agonists.