title: cGMP-dependent protein kinase mediates the reduction of Ca2+ by cAMP in vascular smooth muscle cells.
abstract: The major action of forskolin, the diterpine activator of adenylate cyclase, in primary (unpassaged) rat aortic smooth muscle cells is to reduce vasopressin-stimulated Ca2+ concentrations. In repetitively passaged cells, however, forskolin by itself increased Ca2+ levels by apparently stimulating Ca2+ uptake into the cell and had much smaller effects on inhibiting vasopressin-stimulated Ca2+ elevations. Both primary and passaged smooth muscle cells contained adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase. Guanosine 3',5'-cyclic monophosphate (cGMP)-dependent protein kinase was greatly reduced or absent in passaged smooth muscle cells. The introduction of purified cGMP-dependent protein kinase into the cytoplasm of passaged cells prevented forskolin from elevating intracellular Ca2+ and restored the capacity of forskolin to reduce vasopressin-stimulated Ca2+ mobilization. Similar effects were observed for isoproterenol in passaged smooth muscle cells. When introduced into cells, the active catalytic subunit of the cAMP-dependent protein kinase did not lead to reductions in Ca2+ levels. These results suggest that cAMP elevations lead to profound changes in Ca2+ metabolism through activation of both cAMP- and cGMP-dependent protein kinases. Activation of cGMP-dependent protein kinase by cAMP leads to the reduction in intracellular Ca2+, whereas activation of cAMP-dependent protein kinase may only mediate the uptake of Ca2+ from extracellular sources.
authors.affiliation: Department of Pharmacology, College of Medicine, University of South Alabama, Mobile 36688.
authors.forename: T M
authors.initials: TM
authors.lastname: Lincoln
authors.forename: T L
authors.initials: TL
authors.lastname: Cornwell
authors.forename: A E
authors.initials: AE
authors.lastname: Taylor
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism / Q000502:physiology*; D006152:Cyclic GMP / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008970:Molecular Weight; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D007527:Isoenzymes; D005576:Colforsin; D000242:Cyclic AMP; D011494:Protein Kinases; D006152:Cyclic GMP; D002118:Calcium