title: G-protein regulation of an L-type calcium channel current in canine jejunal circular smooth muscle.
abstract: Calcium entry into smooth muscle cells is essential to maintain contractility. In canine jejunal circular smooth muscle cells the predominant calcium entry pathway is through L-type calcium channels. The aim of this study was to determine the G-protein regulation of L-type calcium channel current (ICaL) in isolated canine jejunal circular smooth muscle cells. Barium (80 mM) was used as the charge carrier. GTP-gamma S and GTP increased maximal inward current from 118.7 +/- 12 pA to 227.5 +/- 21.5 pA (n = 8) and 174.6 +/- 10.1 pA (n = 6) respectively. The increase in inward current was blocked by nifedipine suggesting it was through L-type calcium channels. Pertussis toxin did not alter baseline ICaL while cholera toxin increased ICaL from 125 +/- 19 pA in controls (n = 6) to 347 +/- 30 pA (n = 4). Staurosporine inhibited the increase in current evoked by GTP-gamma S and calyculin further increased ICaL over the increase evoked by GTP-gamma S. The results suggest that cholera toxin sensitive G-proteins activate L-type calcium channels in isolated canine jejunal circular smooth muscle cells through protein phosphorylation.
authors.affiliation: Department of Physiology and Biophysics, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: G
authors.initials: G
authors.lastname: Farrugia
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D002478:Cells, Cultured; D004285:Dogs; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000494:pharmacology; D007583:Jejunum / Q000166:cytology / Q000378:metabolism; D008297:Male; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism*; D010766:Phosphorylation
chemical_list: D015220:Calcium Channels; D006153:Guanosine Diphosphate; D019204:GTP-Binding Proteins