Dormer R L, Poulsen J H, Licko V, Williams J A
Am J Physiol. 1981 Jan;240(1):G38-49. doi: 10.1152/ajpgi.1981.240.1.G38.
45Ca2+ exchange and total calcium content were measured in isolated mouse pancreatic acini. 45Ca2+ uptake could be described as the sum of a constant and a single exponential kinetic component; about 60% of total acinar calcium was exchangeable. Stimulation by bethanechol increased 45Ca2+ uptake, but the time course of uptake could be fit only by the addition of a more rapid kinetic component without any change in the total exchangeable Ca2+. 45Ca2+ washout after 1-h loading could be fit as the sum of two exponential components. Stimulation increased the rate of 45Ca2+ washout with the appearance of a third and more rapid kinetic component. There was not, however, a good correspondence between the exponential constants measured in uptake and washout protocols in unstimulated acini. Exponential constants were also affected by the concentration of calcium in the medium, further indicating the presence of nonlinearities in 45Ca2+ exchange. The dose-response relationships were similar for bethanechol stimulation of 45Ca2+ uptake and amylase release, whereas stimulation of 45Ca2+ washout reached a maximum at a higher concentration of bethanechol. Both 45Ca2+ uptake and analytical measurement of total Ca2+ showed a rapid drop in acinar Ca2+ content followed by a gradual reuptake on stimulation by bethanechol. It is concluded that the initial primary effect of secretagogues is to increase Ca2+ efflux, which is interpreted to be the result of release of sequestered calcium into the cytosol.
在分离的小鼠胰腺腺泡中测量了⁴⁵Ca²⁺交换和总钙含量。⁴⁵Ca²⁺摄取可描述为一个常数和一个单指数动力学成分的总和；约60%的腺泡总钙是可交换的。氨甲酰甲胆碱刺激增加了⁴⁵Ca²⁺摄取，但摄取的时间进程只能通过添加一个更快的动力学成分来拟合，而可交换总钙没有任何变化。加载1小时后的⁴⁵Ca²⁺洗脱可拟合为两个指数成分的总和。刺激增加了⁴⁵Ca²⁺洗脱速率，并出现了第三个更快的动力学成分。然而，在未刺激的腺泡中，摄取和洗脱实验中测量的指数常数之间没有很好的对应关系。指数常数也受培养基中钙浓度的影响，进一步表明⁴⁵Ca²⁺交换中存在非线性。氨甲酰甲胆碱刺激⁴⁵Ca²⁺摄取和淀粉酶释放的剂量-反应关系相似，而刺激⁴⁵Ca²⁺洗脱在较高浓度的氨甲酰甲胆碱时达到最大值。⁴⁵Ca²⁺摄取和总钙的分析测量均显示，腺泡钙含量迅速下降，随后在氨甲酰甲胆碱刺激下逐渐重新摄取。结论是，促分泌剂的初始主要作用是增加Ca²⁺外流，这被解释为是将螯合钙释放到细胞质中的结果。
