Cyclic GMP-dependent stimulation reverses G-protein-coupled inhibition of smooth muscle myosin light chain phosphate.
8-bromo-cyclic guanosine monophosphate (8-br-cGMP), at constant Ca2+, accelerated the dephosphorylation of the regulatory myosin regulatory light chain and relaxation of permeabilized rabbit ileum smooth muscle. These effects were independent of myosin light chain kinase activity. Similarly, 8-br-cGMP relaxed GTPgammaS-induced force and inhibited the GTPgammaS-induced increase in myosin light chain phosphorylation at constant [Ca2+]. We conclude that cyclic GMP-dependent kinase, activated by 8-br-cGMP, increases smooth muscle myosin light chain phosphatase activity and counteracts the inhibition of the latter enzyme by G-protein(s).
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Department of Molecular Physiology and Biological Physics, Charlottesville, Virginia 22908, USA.
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D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism*; D005263:Femoral Artery; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007082:Ileum; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D043263:Myosin-Light-Chain Phosphatase; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011817:Rabbits; D010738:Type C Phospholipases; D001743:Urinary Bladder
D015124:8-Bromo Cyclic Adenosine Monophosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D010749:Phosphoprotein Phosphatases; D043263:Myosin-Light-Chain Phosphatase; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D006152:Cyclic GMP; D002118:Calcium