Effect of Hypocalcemia on Isoproterenol Induced Cardiotoxicity in Dogs

Publisher Website
Google Scholar
Abstract
The effect of serum calcium on the myocardial damages produced by isoproterenol was studied in the dog. Hemodialysis for 80 min in the absence of calcium was used to alter serum calcium concentration in seven experimental animals. The same number of animals were dialysed in the presence of calcium and were used as controls. After hemodialysis all animals were infused with isoproterenol 2.0 μg/kg/min for 4 hours. The myocardial damage was assessed by comparing serial measurements of the serum cardiac enzyme activities CK and CK-MB and the electrocardiographic findings of the two groups, before, during and after isoproterenol infusion. Serum calcium decreased significantly after dialysis only in the experimental group (1.15 vs 2.19 mmolL-1). Total C K activities of the experimental group during and after isoproterenol infusion were 2 to 3 times lower than in the controls (190-360 vs 410-1370 IU.L-1). Changes of the C K-MB isoenzyme activities were more profound, these were detectable and measured only in 4 of the experimental animals and in much lower activities than in the controls (25-61 vs 45-445 IU.L-1). A positive correlation was found (r=0.673, p-1 wet weight). On the contrary magnesium concentration increased respectively. It is concluded that low serum calcium has a protective effect against the cardiotoxic action of isoproterenol. This protective action may be relevant to the decreased calcium and increased magnesium of the heart of the animals hemodialysed in the absence of calcium.