Regulation of one type of Ca2+ current in smooth muscle cells by diacylglycerol and acetylcholine.
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.
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002024:Bufo marinus; D002118:Calcium / Q000378:metabolism*; D004075:Diglycerides / Q000494:pharmacology*; D004594:Electrophysiology; D005989:Glycerides / Q000494:pharmacology*; D007473:Ion Channels / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism
D004075:Diglycerides; D005989:Glycerides; D007473:Ion Channels; D011493:Protein Kinase C; D000109:Acetylcholine; D002118:Calcium