Potassium transport across basolateral membrane of acinar cells in the perfused rat pancreas

Abstract

Efflux and influx of K+ across the basolateral membrane of acinar cells were continuously computed from the change in K+ concentration in the perfusate collected from the portal vein of the isolated perfused rat pancreas. Continuous stimulation with different concentrations of COOH-terminal octapeptide of cholecystokinin (CCK-8) caused characteristic patterns of K+ flux and fluid secretion as follows: 1) stimulation with 10 pM CCK-8 induced a gradual and small increase in K+ influx and sustained fluid secretion; 2) stimulation with 100 pM CCK-8 caused an initial transient K+ efflux followed by a secondary slow K+ influx and sustained fluid secretion; 3) stimulation with 1 nM CCK-8 also induced an initial transient K+ efflux followed by a secondary slow K+ influx, whereas there was only a slight transient increase in fluid secretion. Ouabain abolished the CCK-8-induced K+ influx, but furosemide had little, if any, effect on the CCK-8-induced K+ flux and fluid secretion. Complete replacement of Cl- with equimolar NO3- had little effect on the CCK-8-induced K+ influx. These results suggest that CCK-8 activates not only passive K+ transport but also an ouabain sensitive Na(+)-K+ pump and that the furosemide-sensitive Na(+)-K(+)-2Cl- symport may not play a significant role in CCK-8-induced K+ transport.