AJP - Gastrointestinal and Liver Physiology, Vol 246, Issue 5 484-G491, Copyright © 1984 by American Physiological Society
Release of 86Rb from rat submandibular gland slices: relation to sodium pump activity
D. J. Stewart, M. Laansoo and A. K. Sen
Slices of rat submandibular gland were preloaded with 86Rb, an isotope that
can substitute for K+ in the K+ release process. The efflux of 86Rb was
monitored in a superfusion apparatus that efficiently removed the 86Rb as
it exited from the tissue slices. Carbachol and the calcium ionophore
A23187 activated a calcium-dependent increase in 86Rb efflux. Dibutyryl
cGMP had no detectable effect on 86Rb efflux in contrast to its activation
of ouabain-sensitive uptake of 86Rb observed in an earlier study. The
stimulated release of 86Rb was not dependent on the presence of either
sodium or chloride ions. When 86Rb efflux was stimulated by carbachol, the
efflux rate returned toward the basal rate after a few minutes of exposure
to carbachol in the medium. If ouabain was then introduced into the
superfusate, a large increase in efflux was stimulated. In the absence of
carbachol, only a small increase in 86Rb efflux was stimulated by ouabain.
The effect of ouabain indicates that there was a substantial recycling of
86Rb between the release and uptake processes in the extracellular space of
the tissue slice. The significance of this observation is discussed.
