title: Skinned coronary smooth muscle: calmodulin, calcium antagonists, and cAMP influence contractility.
abstract: The effects of Ca2+, calmodulin, cAMP, the catalytic subunit of cAMP-dependent protein kinase (CSU) and some Ca2+ antagonists were studied in chemically (Triton X-100) skinned coronary smooth muscle. Calmodulin increased the Ca2+ responsiveness of the muscle fiber as indicated by the reduction in the threshold as well as the half-maximal activating Ca2+ concentration. Trifluoroperazine, a calmodulin antagonist, inhibited Ca2+-calmodulin-induced contraction. Both cAMP and CSU were effective inhibitors of contraction induced at an intermediate Ca2+ concentration. Fendiline, a Ca2+-antagonist, at 2 x 10(-4) M produced a significant inhibitory effect, which was reduced by increasing the Ca2+ concentration. From other Ca2+ antagonists tested, W-7, but not D600 and verapamil, produced some inhibitory effect. The data indicate that the response of skinned coronary smooth muscle to Ca2+, calmodulin and cAMP are similar to those obtained with other skinned smooth muscles. Furthermore, skinned fiber preparation can serve as a useful tool to investigate possible direct effects of drugs on the activating and regulatory systems in smooth muscle.
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002147:Calmodulin / Q000502:physiology*; D003331:Coronary Vessels; D000242:Cyclic AMP / Q000502:physiology*; D003864:Depression, Chemical; D005275:Fendiline / Q000494:pharmacology; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D013552:Swine; D014268:Trifluoperazine / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D002147:Calmodulin; D014268:Trifluoperazine; D000242:Cyclic AMP; D005275:Fendiline; D002118:Calcium