PEPTIDE-EVOKED RELEASE OF AMYLASE FROM ISOLATED ACINI OF THE RAT PAROTID-GLAND

Departments oS1Medical Physiology and iMedicnl Analonly B, the Panum m stitute, Uiliversity oS Copenhageil, Blegdamsvej 3, Investigations of the effects of the neuropeptides, substance P (SP), neurokinin A (NKA) , neuropeptide K (NPK), gastrin releasing peptide (GRP), calcitonin ge ne related peptide (CGRP) and vasoactive intestinal peptide (VIP), and of acetylcholine on amylase secretion have been carried out on isolat ed acini of the rat parotid gland. Furthermore, the occurrence and loc ation of the peptides in the gland was studied. Finally, binding of I- 125-BH-Sp to, isolated acini were studied in order to characterize the ir tachykinin receptor(s) and their binding kinetics. Only SP, NKA, NP K and VIP stimulated amylase release. VIP, however, with a rather low potency (EC(50) at 155 nmol/l), Simultaneous stimulation with two comp ounds elicited additive responses, except for VIP and acetylcholine wh ich elicited an effect significantly above additive response. Only SP, NKA, VIP and CGRP could be identified in extracts of the gland. The i mmunoreactivity of these peptides could be located to varicose nerve f ibers in the gland. Binding of labeled SP to the isolated acini exhibi ted the characteristics of a genuine agonist/receptor interaction, and the rank order of displacement potencies indicated the presence of NK 1-receptors. Thus, the results of the present study support previous s uggestions that the tachykinins and VIP are likely to be involved in a mylase secretion in the rat parotid gland.