Effect in vivo of β-adrenergic stimulation, angiotensin II, dibutyryl cyclic AMP, and theophylline on tonin concentration in rat saliva and submaxillary gland

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Abstract
Tonin (an enzyme present in rat submaxillary gland and saliva) was previously shown to be able, unlike renin and reninlike substances, to release angiotensin II either directly by acting on an appropriate substrate or from angiotensin I. Administration of a .beta.-adrenergic drug, isoproterenol, produces a rise of tonin concentration in saliva without affecting its concentration in the submaxillary gland. Prior administration of a .beta. blocker, propranolol, partially prevents this effect. Administration of theophylline increases tonin concentration in saliva and the submaxillary gland, whereas dibutyryl cyclic[c]AMP increases tonin concentration in the former. .beta.-Adrenergic stimulation apparently enhances tonin release into the saliva and tonin synthesis in the submaxillary gland, and these effects might be mediated by cAMP. Infusion of angiotensin II blocked the stimulatory effect of isoproterenol on salivary tonin. 1Sar-8Ile-angiotensin II is a weak antagonist of angiotensin II in this respect and a strong agonist in terms of blocking the effect of isoproterenol, another role mirrored in other physiological mechanisms of derivatives of angiotensin II.