AJP - Gastrointestinal and Liver Physiology, Vol 238, Issue 6 491-G494, Copyright © 1980 by American Physiological Society
Effect of glucagon on ion transport in mouse intestine
M. E. Kaufman, M. A. Dinno and K. C. Huang
Effects of glucagon (GN) on short-circuited mouse intestine were studied.
GN (30 microgram . ml-1), added to the serosa of intestine mounted in an
Ussing chamber and bathed in glucose-free Ringer, induced significant
increases of 43% in serosal-to-mucosal Cl- flux (Js leads to m Cl), 315% in
net Cl- secretion (Jnet Cl), 85% in net residual flux (J net R), 61% in
short-circuit current (Isc), and 44% in open-circuit potential difference
(PD). The mucosal-to-serosal Cl- flux and both unidirectional Na+ fluxes
(Jm leads to s Na and Js leads to m Na) were unchanged. In a glucose Ringer
bathing medium, GN exhibited no significant effects on ion fluxes and
electrical parameters. To eliminate the possibility that observed
GN-induced changes in PD and Isc were partially due to changes in membrane
surface charge, the effects of GN in Cl- -free Ringer were studied. Under
these conditions, GN had no effect on electrical parameters. Furthermore,
GN elicited no effect on cAMP levels in either the presence or absence of
glucose. These findings suggest that 1) the effect of GN on Jnet Cl is
masked in the presence of glucose, 2) GN-induced increases in Isc and PD
are a reflection of the increase in Jnet Cl and are neither due to changes
in membrane surface charge nor to an increase in net Na+ flux, and 3)
GN-induced secretory diarrhea is in part due to changes in electrolyte
transport.
