RED CELL ZINC AND RED CELL ZINC METALLOENZYMES IN HYPERTHYROIDISM

Abstract

ABSTRACT The activity of the following zinc metalloenzymes was measured in the erythrocytes of hyperthyroid patients: malic dehydrogenase (MDH), aldolase (ALD), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), alcohol dehydrogenase (ADH), and lactic dehydrogenase (LDH). A significant increase in the activities of ADH (0.8 ± 0.3 μmoles per min per g of haemoglobin) and GAPDH (30.5 ± 13.4) was found; the control values being 0.5 ± 0.3 and 7.6 ± 4.6 respectively. The activities of ALD, MDH, and of LDH were not significantly different from those of the control group. The mean red cell zinc in the hyperthyroid group was 31.6 ± 6.2 μg per g of haemoglobin in contrast to 50.4 ± 8.1 in the control group. It is concluded that none of the zinc metalloenzymes measured accounts for the diminution of erythrocyte zinc occurring in hyperthyroidism, a phenomenon that should be attributed to the inhibition of carbonic anhydrase B as reported previously.