The effects of L-alanine and acetylcholine on membrane potential, 45Ca2+ and 86Rb+ efflux and amylase secretion in the isolated mouse pancreas.

A comparative study was made of the effects of acetylcholine (ACh) and the neutral amino acid L-alanine on membrane potential, 45Ca2+ and 86Rb+ fractional efflux, and amylase secretion in segments of the isolated mouse pancreas. Both ACh and L-alanine evoked similar dose-dependent depolarizations of pancreatic acinar cells. ACh, but not L-alanine, caused a marked reduction in input resistance and evoked electrical uncoupling of acinar cells at high concentrations. Measurements of 45Ca2+ release from pre-labelled tissue showed that ACh increased the fractional efflux of 45Ca2+ whereas L-alanine had no such effect. Both ACh and L-alanine stimulated the release of 86Rb+ from pre-labelled tissues. The L-alanine-evoked 86Rb+ efflux was markedly reduced by pre-treatment with 10(-3) M ouabain which had no effect on the ACh-induced response. L-alanine had no significant effect on amylase secretion whereas ACh elicited a marked increase in amylase output. These results show that although both ACh and L-alanine evoke depolarization of the pancreatic acinar cell membrane, the mechanisms underlying their actions on the cells are different.