title: Effect of forskolin on phosphorylation of a 25,000 Mr protein in perfused guinea pig hearts.
abstract: The effects of forskolin on phosphorylation of proteins of a 100,000 X g fraction was examined in isolated beating guinea pig hearts. Hearts were perfused with [32P] inorganic phosphate to label intracellular adenine nucleotides. Forskolin was injected into the coronary circulation and after freeze-clamping, phosphorylated proteins in a fraction were separated by sodium dodecyl sulfate-polyacrylamide gel electro-phoresis. Forskolin increased the incorporation into a 25,000 Mr protein approximately 15 fold over control. Incorporation of label was time and dose dependent and was temporally coincident with increases in developed tension. A sarcolemmal fraction prepared from perfused hearts contained a similar 25,000 Mr protein. The data provides evidence that forskolin induced inotropy is accompanied by cAMP-dependent protein kinase mediated phosphorylation. The phosphorylation may be of the same protein whose phosphorylation is associated with epinephrine-induced increase in contractility.
mesh_terms: D000067956:Adenylyl Cyclase Inhibitors; D000818:Animals; D005576:Colforsin; D004224:Diterpenes / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D004837:Epinephrine / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008566:Membranes / Q000378:metabolism; D008970:Molecular Weight; D009124:Muscle Proteins / Q000378:metabolism*; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D010766:Phosphorylation; D012508:Sarcolemma / Q000378:metabolism; D012967:Sodium Dodecyl Sulfate
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D004224:Diterpenes; D009124:Muscle Proteins; D005576:Colforsin; D012967:Sodium Dodecyl Sulfate; D004837:Epinephrine