[Protective effects of cyproheptadine on calcium paradox in isolated rat hearts]

The protective effects of cyproheptadine, an antiserotonin-antihistaminic agent with calcium channel blocker activity, on calcium paradox in isolated Langendorff's heart in rats were studied. After a 5 min of calcium-free perfusion [standard Krebs-Henseleit (K-H) buffer without calcium, gassed with 95% O2 and 5% CO2] followed by a 20 min of normal K-H buffer (Ca2+ 2.5 mmol/L) perfusion, extensive and rapid myocardial injury was observed: release of massive cellular enzymes such as lactic dehydrogenase (LDH) and creatine phosphokinase (CPK), significant decrease of myocardial anti-oxygen free radical enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities but no obvious change of myocardial lipid peroxides such as malondialdehyde (MDA) content was observed. The loss of normal colour and mechanical activity, even contracture, was also observed in the injured hearts. Cyproheptadine (2.5-5 mumol/L) was shown to effectively antagonize the damage. The results suggest that the protective effects of cyproheptadine on the calcium paradox may be related to its actions of blocking calcium channel, protecting anti-oxygen free radical enzymes and scavenging oxygen free radicals in the myocardial tissues.