[Serum creatine kinase. II. Experiences in myocardial infarct and other cardiologic diseases using the activated reverse reaction]

Effect of hypocalcemia on isoproterenol induced cardiotoxicity in dogs

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 micrograms/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 mmol X L-1). Total CK 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 X L-1). Changes of the CK-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 X L-1). A positive correlation was found (r = 0.673, p less than 0.05) between the highest value of CK-MB of both groups and the serum calcium concentration after hemodialysis. In accordance to the differences of the biochemical estimates the effect of serum calcium on the cardiotoxic effect of isoproterenol has been further emphasized by the electrocardiographic findings. Thus arrhythmias, negative T-waves and significant ST segment depression were observed only in one experimental animal. In contrast these electrocardiographic disturbances were common and marked findings in all but one of the control animals. In both groups these electrocardiographic findings were reversed one to three hours after the termination of the isoproterenol infusion. Myocardial calcium at the end of the experiment was lower in the experimentals compared to the controls (0.23 vs 0.30 mmol X kg-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.

The Szasz-ratio (CK/GOT) as example for the diagnostic significance of enzyme ratios in serum

The diagnostic significance of enzyme and isoenzyme ratios in serum relies on their different distribution at various levels: from organs to subcellular structures. Factors which modify the ratios are the molecular properties of enzymes and isoenzymes and their turnover in the cells and in the extracellular space. These pathophysiological principles are considered with respect to the Szasz ratio CK/GOT and its application for the differential diagnosis of acute myocardial infarction.