The mechanisms by which @entity413 regulates @entity460 fluxes in pancreatic endocrine cells were investigated by monitoring the efflux of 45Ca from prelabeled and perifused @entity35 pancreatic islets. In the absence of both extracellular @entity460 and @entity413 , partial or total removal of extracellular @entity1372 decreases the efflux of 45Ca from prelabeled islets. @entity413 also reduces the efflux of 45Ca from islets perifused in the absence of extracellular @entity460 . This inhibitory effect of @entity413 on 45Ca efflux is decreased by half when the extracellular concentration of @entity1372 is lowered to 24 mM. In the absence of extracellular @entity460 but presence of @entity413 , partial or even total removal of extracellular @entity1372 fails to decrease the efflux of 45Ca. At normal extracellular @entity460 concentration (1 mM) partial removal of extracellular @entity1372 dramatically increases 45Ca efflux from pancreatic islets. This increase in 45Ca efflux is partially but not totally suppressed by either 16.7 mM @entity413 or @entity1953 . It is totally suppressed by 4.4 mM @entity413 or by the combination of 16.7 mM @entity413 and @entity1953 . At normal extracellular @entity460 concentration, @entity413 initially reduces and subsequently increases 45Ca efflux. The initial fall is unaffected by @entity1022 but decreased by 50% at low extracellular @entity1372 concentration (24 mM). The present results suggest the existence in pancreatic endocrine cells of a @entity413 -sensitive process of @entity1372 - @entity460 counter-transport. By inhibiting such a process, @entity413 may decrease the efflux of @entity460 from islet cells. The effect of @entity413 is not mediated by an increase in intracellular @entity1372 concentration. It could contribute to the intracellular accumulation of @entity460 which is thought to trigger insulin release.

Regulation of @entity460 fluxes in @entity35 pancreatic islets: XXXX extrusion by @entity1372 - @entity460 countertransport.

@entity1022 :: ('MESH:D013779', 'Chemical') :: ['tetrodotoxin'] @entity1372 :: ('MESH:D012964', 'Chemical') :: ['sodium'] @entity460 :: ('MESH:D002118', 'Chemical') :: ['calcium'] @entity35 :: ('10116', 'Species') :: ['rat'] @entity1953 :: ('MESH:D003035', 'Chemical') :: ['cobalt'] @entity413 :: ('MESH:D005947', 'Chemical') :: ['glucose', 'Glucose']
@entity460 :: (MESH:D002118,Chemical) :: ['calcium']
