Potassium ions and the secretion of insulin by islets of Langerhans incubated in vitro.
1. A method was devised for the isolation of islets of Langerhans from rabbit pancreas by collagenase digestion in order to study the influx and efflux of K(+) in islets during insulin secretion. 2. Glucose-induced insulin release was accompanied by an increased rate of uptake of (42)K(+) by the islets of Langerhans, though this was not the case for secretion in response to tolbutamide. Ouabain significantly inhibited the uptake of (42)K(+) by islet tissue. 3. No significant increase in the rate of efflux of (42)K(+) was demonstrated during active insulin secretion. 4. Slices of rabbit pancreas were incubated in media of different K(+) content, and rates of insulin release were determined. Alteration of the K(+) concentration of the medium between 3 and 8mm had no effect on the rate of insulin release by pancreas slices. However, decrease of the K(+) concentration to 1mm resulted in inhibition of secretion in response to both glucose and to tolbutamide. Conversely, an increase in K(+) concentration increased rates of insulin release in response to both these stimuli. 5. It is concluded that, though unphysiological concentrations of K(+) may influence the secretion of insulin, fluxes of K(+) in the islets do not appear to be important in the initiation of insulin secretion.
D000818:Animals; D003864:Depression, Chemical; D005947:Glucose / Q000494:pharmacology; D007118:Immunoassay; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007456:Iodine Isotopes; D007515:Islets of Langerhans / Q000378:metabolism*; D007930:Leucine / Q000378:metabolism; D008297:Male; D008722:Methods; D003012:Microbial Collagenase; D010042:Ouabain / Q000494:pharmacology; D010179:Pancreas / Q000032:analysis / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D011194:Potassium Isotopes; D011817:Rabbits; D013268:Stimulation, Chemical; D014044:Tolbutamide / Q000494:pharmacology; D014316:Tritium
D007328:Insulin; D007456:Iodine Isotopes; D011194:Potassium Isotopes; D014316:Tritium; D010042:Ouabain; D014044:Tolbutamide; D003012:Microbial Collagenase; D007930:Leucine; D005947:Glucose; D011188:Potassium