AJP - Gastrointestinal and Liver Physiology, Vol 238, Issue 5 440-G444, Copyright © 1980 by American Physiological Society
Inhibition of pancreatic alpha-aminoisobutyric acid uptake by cholecystokinin and other secretagogues
Y. Iwamoto and J. A. Williams
The uptake of the non-metabolizable amino acid, alpha-aminoisobutyric acid
(AIB), by isolated mouse pancreatic acini was studied. AIB was concentrated
in acinar cell water by an Na+-dependent mechanism. The protein hormone
secretagogues caerulein, cholecystokinin, and gastrin and the cholinergic
agent carbachol inhibited AIB uptake by greater than 50% of control. The
effect of secretagogues on AIB uptake was maximal at hormone concentrations
that are slightly higher than those that are maximal for amylase release,
but comparable to those concentrations that maximally increase glucose
transport by acini. This inhibition of AIB uptake was mediated by both
inhibition of AIB influx and stimulation of AIB efflux. In the presence of
Ca2+, the Ca2+ ionophore A23187 mimicked the effect of caerulein on AIB
uptake. In the absence of Ca2+, control AIB uptake was markedly decreased
and both caerulein and A23187 had no further effects. It was concluded,
therefore, that secretagogues known to induce enzyme release by an effect
on cellular Ca2+ also decrease AIB uptake and that this effect on uptake is
most likely mediated by Ca2+.
