Morgan N G, Rumford G M, Montague W
Biosci Rep. 1985 Dec;5(12):1053-60. doi: 10.1007/BF01119626.
Noradrenaline caused a prompt but transient increase in the rate of 45Ca2+ efflux from isolated rat islets of Langerhans perifused in Ca2+ depleted medium. The response was modest in size and was unaffected by isosmotic replacement of NaCl with choline chloride or by inclusion of 0.5 mM dibutyryl cAMP in the perifusion medium, suggesting that it was not mediated by Na+: Ca2+ exchange nor by lowered cAMP. Despite its effect on 45Ca2+ efflux, noradrenaline treatment did not alter the kinetics of 45Ca2+ efflux in response to the muscarinic agonist, carbamylcholine, nor did it change the magnitude of the response to this agent. Simultaneous introduction of 20 mM glucose with noradrenaline prevented a rise in 45Ca2+ efflux and indeed resulted in inhibition of 45Ca2+ efflux. The data suggest that noradrenaline does not directly activate the mechanisms which regulate Ca2+ extrusion from islets cells, and they do not support a primary role for the Ca2+ efflux response in mediating adrenergic inhibition of insulin secretion.
去甲肾上腺素使在缺钙培养基中灌流的离体大鼠胰岛的45Ca2+流出速率迅速但短暂地增加。该反应规模适度，不受用氯化胆碱等渗替代氯化钠或在灌流培养基中加入0.5 mM二丁酰环磷腺苷的影响，这表明它不是由Na+:Ca2+交换介导的，也不是由降低的环磷腺苷介导的。尽管去甲肾上腺素对45Ca2+流出有影响，但去甲肾上腺素处理并未改变对毒蕈碱激动剂氨甲酰胆碱的45Ca2+流出动力学，也未改变对该药物反应的幅度。同时引入20 mM葡萄糖和去甲肾上腺素可防止45Ca2+流出增加，实际上还导致45Ca2+流出受到抑制。数据表明，去甲肾上腺素不会直接激活调节胰岛细胞Ca2+外排的机制，并且它们不支持Ca2+流出反应在介导肾上腺素能抑制胰岛素分泌中起主要作用。
