Atrial natriuretic factor modifies the composition of induced-salivary secretion in the rat

We have previously reported that although the atrial natriuretic factor (ANF) was not a sialogogic agonist, it enhanced cholinergic, a-adrenergic and peptidergic (substance P) stimulated salivation in the submaxillary and parotid gland of the rat. The purpose of the present work was to study whether ANF modified the composition of agonist-induced saliva in the rat. Results showed that in the submaxillary gland, ANF increased sodium and decreased potassium excretion when salivation was stimulated by methacholine (MC) or substance P (SP). However, when salivation was induced by methoxamine (MX), ANF only increased sodium excretion. On the other hand, in the parotid gland, ANF increased both sodium and potassium excretion when salivation was induced either by MC or SP but did not modify electrolyte output in MX induced salivary secretion. Protein output and amylase activity were not modified by the presence of ANF when the aforementioned sialogogic agonists were used to elicit salivation in either gland. Although ANF did not modify the volume of isoproterenol (IF) induced saliva, it increased protein output in both glands and it increased amylase activity in the parotid gland. The present results suggest that ANF may play a role in the modulation of salivary secretion in the parotid and submaxillary glands of the rat. ANF effect is likely to be mediated by modifications in the calcium level linked to phosphoinositide metabolism within the acinar and/or the ductal cells of the salivary glands.