Changes in biochemical properties of myocardial lactate dehydrogenase during exposure of rats to high altitude.

Exposure of normal rats to chronic natural hypoxia has shown the following effect upon catalytic properties of myocardial lactate dehydrogenase (LDH): significant increase of the two substrates pyruvate and lactate in tissue extracts; no changes in electrophoretic patterns of the enzyme; a slight enhancement of the activation energy of enzyme molecules; a significant increase in the Michaelis constant for pyruvate. Variations in biochemical properties of LDH appear after 12 ueeks of life in high altitude environment. These adjustments may be related to the stimulation of anaerobic metabolism induced by altitudinal hypoxia. Changes in LDH biochemical parameters seem adaptative.