Handwerger S, Conn P M, Barrett J, Barry S, Golander A
Am J Physiol. 1981 May;240(5):E550-5. doi: 10.1152/ajpendo.1981.240.5.E550.
To study the effects of calcium on the release of human placental lactogen (hPL), placental explants were exposed to media containing lower or higher concentrations of calcium than normally available to the placenta. Explants exposed for 2 h to calcium-poor medium or medium containing either 2 mM EDTA or 2 mM EGTA released 160, 248, and 253% more hPL, respectively, than control explants. In contrast, explants exposed to medium containing higher than normal calcium concentrations released the same amounts of hPL as the control explants. At lower than normal extracellular calcium concentrations, the increased hPL release was inversely proportional to the calcium concentration. The increased release in calcium-poor medium was inhibited by subsequent exposure of the explants to medium containing calcium and was prevented by either barium or magnesium. Changes in barium or magnesium concentrations, however, had no effects on hPL release in the presence of normal extracellular calcium concentrations. Methoxyverapamil (D 600), an inhibitor of calcium flux, stimulated hPL release. Because low extracellular calcium and methoxyverapamil both inhibit calcium influx, these experiments suggest that calcium influx inhibits hPL release. The role of calcium in the regulation of hPL release therefore appears to be different from that reported in other release systems.
为了研究钙对人胎盘催乳素（hPL）释放的影响，将胎盘外植体暴露于钙浓度低于或高于胎盘正常可利用浓度的培养基中。与对照外植体相比，暴露于缺钙培养基或含有2 mM乙二胺四乙酸（EDTA）或2 mM乙二醇双乙醚二胺四乙酸（EGTA）的培养基中2小时的外植体，分别释放出多160%、248%和253%的hPL。相反，暴露于钙浓度高于正常水平的培养基中的外植体释放的hPL量与对照外植体相同。在低于正常细胞外钙浓度时，hPL释放增加与钙浓度成反比。在缺钙培养基中释放增加，通过随后将外植体暴露于含钙培养基而受到抑制，并且被钡或镁所阻止。然而，在存在正常细胞外钙浓度的情况下，钡或镁浓度的变化对hPL释放没有影响。钙通量抑制剂甲氧基维拉帕米（D 600）刺激hPL释放。由于低细胞外钙和甲氧基维拉帕米均抑制钙内流，这些实验表明钙内流抑制hPL释放。因此，钙在hPL释放调节中的作用似乎与其他释放系统中报道的不同。
