Regulation of one type of Ca2+ current in smooth muscle cells by diacylglycerol and acetylcholine |
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Authors: | M B Vivaudou L H Clapp J V Walsh J J Singer |
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Affiliation: | Department of Physiology, University of Massachusetts Medical School, Worcester 01655. |
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Abstract: | 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. |
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