Lactate dehydrogenase and isoenzyme changes in rats with experimental thiamine deficiency.

Heat and liver lactate dehydrogenase (LDH) and isoenzyme distributions were studied in rats with experimental thiamine deficiency. No change in total heart LDH activity was observed on days 24 and 40 of a thiamine deficient diet. At the time of symptoms (average 53 days on diet), total heart muscle LDH was slightly decreased in thiamine deficient rats (248 +/- 12 U/g tissue, Mn +/- SE) compared to ad lib fed controls (293 +/- 12, p less than 0.05), but did not differ from pair fed controls (273 +/- 15). Heart muscle LDH isoenzyme distribution showed a relative increase in the H4 band and a decrease in the H2M2 and HM3 bands in thiamine deficiency on day 24. This pattern became more promient by day 40. Calculated total M-LDH activity of heart muscle in thiamine deficient rats was significantly decreased at day 40 (44 +/- 3) compared to pair fed controls (57 +/- 5, p less than 0.05) and ad lib fed controls (85 +/- 7 p less than 0.001). Further changes were not observed in the symptomatic stage. Total H-LDH in heart muscle did not change during the period of study, while total liver LDH activity was reduced in thiamine deficient rats at the symptomatic stage (137 +/- 15) compared with pair fed controls (193 +/- 12, p less than 0.05) and ad lib fed controls (407 +/- 50, p less than 0.01). Liver isoenzyme electrophoresis showed an almost 100% distribution to the M4 band. The present investigation demonstrates a decrease in cardiac muscle M-LDH in experimental thiamine deficiency. Differences in LDH isoenzyme distribution in chronic hypoxia and thiamine deficiency are discussed.