Henquin J C, de Miguel R, Garrino M G, Hermans M, Nenquin M
FEBS Lett. 1985 Jul 22;187(1):177-81. doi: 10.1016/0014-5793(85)81237-0.
The mechanism whereby nutrient insulin secretagogues decrease 45Ca2+ efflux from islet cells is controversial. It was studied with mouse islets perifused with Ca2+-free solutions. In the presence of Na+, glucose and ketoisocaproate inhibited 45Ca2+ efflux by about 50%. Substitution of choline+ salts for Na+ salts decreased the efflux rate by 45%, but did not prevent glucose from decreasing it further. Ketoisocaproate also inhibited 45Ca2+ efflux, but less markedly than in an Na+ medium. Omission of Na+ decreased the efflux rate even when it was already lowered by glucose or ketoisocaproate. It is thus clear that nutrient insulin secretagogues decrease 45Ca2+ efflux from islet cells by a mechanism other than the inhibition of the Na+-Ca2+ countertransport, possibly by increasing sequestration of the ion in cellular organelles.
营养性胰岛素促分泌剂降低胰岛细胞45Ca2+外流的机制存在争议。我们使用用无钙溶液灌流的小鼠胰岛对此进行了研究。在有Na+存在的情况下，葡萄糖和酮异己酸抑制45Ca2+外流约50%。用胆碱盐替代钠盐可使外流速率降低45%，但并不能阻止葡萄糖进一步降低外流速率。酮异己酸也抑制45Ca2+外流，但不如在Na+介质中明显。即使外流速率已经因葡萄糖或酮异己酸而降低，去除Na+仍会降低外流速率。因此很明显，营养性胰岛素促分泌剂通过抑制Na+-Ca2+逆向转运以外的机制降低胰岛细胞45Ca2+外流，可能是通过增加细胞器中离子的螯合作用。
