title: Clofibrate, calcium and cardiac muscle.
abstract: The anti-hyperlipidemic drug clofibrate produces negative inotropic effects and arrythmias in isolated perfused rabbit heart Langendorff preparations. In electrically stimulated rat left atria, clofibrate produces negative inotropic effects, the speed of onset and extent of which are decreased by raising the Ca concentration of the bathing medium. Sensitivity of isolated rat atria to clofibrate is not increased when the tissues are stimulated under slow Ca channel conditions, in which the tissues are activated by either isoproterenol or dibutyryl cyclic AMP, although sensitivity to clofibrate is decreased when atria are exposed to increasing concentrations of norepinephrine. Increasing the stimulation frequency of isolated guinea-pig atria to produce a positive treppe also decreases the inhibitory effect of clofibrate, while in rat atria the typical negative treppe is altered towards a positive treppe in presence of clofibrate. The effects of paired electrical stimulation are not diminished by the drug, suggesting that Ca release from the sarcoplasmic reticulum is not affected by clofibrate, although the drug inhibits the rate of Ca uptake by isolated cardiac sarcoplasmic reticulum and mitochondria. These results suggest that clofibrate has multiple effects on Ca functions in cardiac muscle.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002994:Clofibrate / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008929:Mitochondria, Heart / Q000378:metabolism; D009200:Myocardial Contraction / Q000187:drug effects; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
chemical_list: D007473:Ion Channels; D002994:Clofibrate; D007545:Isoproterenol; D002118:Calcium