Vivaudou M B, Clapp L H, Walsh J V, Singer J J
Department of Physiology, University of Massachusetts Medical School, Worcester 01655.
FASEB J. 1988 Jun;2(9):2497-504. doi: 10.1096/fasebj.2.9.2453389.
Electrophysiological recordings from freshly dissociated smooth muscle cells from the stomach of the toad Bufo marinus revealed two types of Ca2+ currents. One has a low threshold of activation and inactivates rapidly; the other has a high threshold of activation and inactivates more slowly. Acetylcholine (ACh) increased the high-threshold current but not the low-threshold current. The synthetic diacylglycerol analog sn-1,2-dioctanoylglycerol, an activator of protein kinase C (PKC), mimicked these effects of ACh on Ca2+ currents. However, another diacylglycerol analog, 1,2-dioctanoyl-3-thioglycerol, which has a closely related structure but does not activate PKC, failed to increase the Ca2+ current. The same was true of 1,2-dioctanoyl-3-chloropropanediol, an analog that even at high concentrations only minimally activates PKC. These results suggest that diacylglycerol may be the second messenger mediating the effects of ACh on one type of voltage-activated Ca2+ channel, possibly by activating PKC.
对从海蟾蜍胃中新鲜分离的平滑肌细胞进行的电生理记录显示出两种类型的Ca2+电流。一种具有低激活阈值且快速失活；另一种具有高激活阈值且失活更慢。乙酰胆碱（ACh）增加了高阈值电流，但未增加低阈值电流。合成二酰基甘油类似物sn-1,2-二辛酰甘油是蛋白激酶C（PKC）的激活剂，模拟了ACh对Ca2+电流的这些作用。然而，另一种二酰基甘油类似物1,2-二辛酰基-3-硫代甘油，其结构密切相关但不激活PKC，未能增加Ca2+电流。1,2-二辛酰基-3-氯丙二醇也是如此，该类似物即使在高浓度下也仅能微弱激活PKC。这些结果表明二酰基甘油可能是介导ACh对一种电压激活型Ca2+通道作用的第二信使，可能是通过激活PKC来实现的。
