Effect of Na+, K+ and Mg2+ on 45Ca+ uptake by pancreatic islets.
Microdissected pancreatic islets of noninbred ob/ob-mice were used to study ionic effects on the lanthanum-nondisplaceable 45Ca2+ uptake by islet cells. Omission of Mg2+ from the incubation medium had no effect, but the 45Ca2+ uptake was increased by omission of Na+ and decreased by omission of K+. Excess Mg2+ (1.2--15 mM) inhibited and excess K+ (4.7--25 mM) stimulated the 45Ca2+ uptake in a concentration-dependent manner. Stimulation of 45Ca2+ uptake in Na+-deficient islets was associated with an enhancement of the basal insulin release. Total abolishment of glucose-stimulated 45Ca2+ uptake in K+-deficient islets did not preclude a significant secretory reponse to glucose. It is concluded that the lanthanum-nondisplaceable 45Ca2+ uptake shows a partial correlation to insulin release.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007811:Lanthanum / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology*; D051379:Mice; D011188:Potassium / Q000494:pharmacology*; D012964:Sodium / Q000494:pharmacology*
D007328:Insulin; D007811:Lanthanum; D012964:Sodium; D008274:Magnesium; D005947:Glucose; D011188:Potassium; D002118:Calcium