Inhibitory Influence of Amino Acids on Secretagogues Induced Exocrine Secretion in Isolated Perfused Rat Pancreas

Abstract

Influence of amino acids upon pancreatic exocrine secretion has been investigated in the isolated perfused pancreas of rats. Arg produced significant and dose-related inhibition of pancreatic juice flow, protein output and amylase output evoked by CCK-PZ (1.25pM). The secretory response evoked by CCK-PZ was inhibited by other amino acids (Ala, Asp, Asn, Gly, Ile, Leu, Lys, Met, Phe, Pro, Thr, Trp, Val, in each 20mM). A similar inhibitory pattern was observed using 10 mixed amino acids of 2mM each (Pro, Phe, Thr, Met, Lys, Asp, Leu, Trp, Val, Gly). Gly at a concentration of 20mM produced significant inhibition of exocrine secretion evoked by ACh (50nM) or GRP (36 pM). The inhibitory response induced by amino acids could not be repeated by using exogenous insulin (1μM) and glucagon (280nM). The inhibitory response was also not changed by increased extracellular Ca (5 or 10mM). However, Gly (20mM) produced inhibition of exocrine secretion evoked by Ca reintroduction into a pancreas which was pretreated with A 23187. It was suggested that the inhibitory effects of some amino acids on exocrine secretion are mainly caused by suppression of Ca influx in a stimulus-secretion coupling process.