PROTEIN SECRETION FROM RAT SUBMANDIBULAR ACINI AND GRANULAR DUCTS - EFFECTS OF EXOGENOUS VIP AND SUBSTANCE-P DURING PARASYMPATHETIC NERVE-STIMULATION

The influences of exogenous vasoactive intestinal peptide (VIP) and su bstance P on the release of peroxidase from acini and true tissue kall ikrein (rK1) from granular ducts of the rat submandibular gland were s tudied during continuous parasympathetic stimulation. Parasympathetic nerve impulses caused a moderate flow of saliva (mean +/- SD, 108 +/- 26 mu l/g tissue/min) that had a low protein concentration (174 +/- 88 mu g/ml). The outputs of peroxidase and rK1 were minimal (14.3 +/- 11 .8 pmol DCF/g tissue/min and 6.5 +/- 3.4 nmol AFC/g tissue/min, respec tively). When administered intravenously, VIP had no apparent effect o n the overall flow rate, but caused a significant increase in the outp ut of peroxidase; 450% at 1 mu g/kg and a further 10-fold increase at 10 mu g/kg. In contrast, substance P (1 mu g/kg) evoked a marked incre ase in flow rate (68%), and peroxidase secretion increased only 3-fold . The output of rK1 was unaffected by either VIP or substance P. Our r esults support the hypothesis that acinar, but not granular duct, prot ein secretion is evoked by non adrenergic, non-cholinergic peptides re leased from parasympathetic nerve terminals. (C) 1998 Elsevier Science Inc.