THE ESTIMATION OF LACTATE DEHYDROGENASE ACTIVITY OF HUMAN ERYTHROCYTES

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Abstract
The influence of pH, temperature, and the concentrations of substrate, coenzyme, and enzyme on the estimation of the lactic dehydrogenase (LDH) activity of human erythrocytes have been examined. The activity had a broad optimum pH range of 7.0 to 7.8 and was markedly influenced by temperature. The optimum concentrations of pyruvate and reduced diphosphopyridine nucleotide (DPNH) were found to be 1.7 X 10-6 and 0.8 X 10-7 mole/ml of incubation mixture respectively. A method for the measurement of LDH activity at optimum conditions (except for temperature) is described. The method was satisfactory over a 10-fold range of enzyme concentration. Of the anticoagulants commonly used in clinical laboratories for collecting blood, oxalate was inhibitory and heparin, fluoride, versene, and citrate had no influence on LDH activity. Enzyme stability studies indicated that whole blood at 4[degree]C and dilute hemolyzate frozen at -10[degree]C could be kept for 4 weeks without loss of LDH activity. Dilute hemolyzate was less stable than whole blood at the same temperature.

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