Abstract
Thiamine-deficient rats have a striking decrease in liver and muscle α-glycerophosphate dehydrogenase activity. When the deficiency was induced with oxythiamine or pyrithiamine the decrease in enzyme was proportional to the dose administered. At equivalent levels, oxythiamine was less effective than pyrithiamine. For lactic dehydrogenase the decrease in activity was less pronounced in dietary deficiency but oxythiamine was more effective in lowering this enzyme concentration. It is concluded that this represents a true effect of thiamine deficiency and not of starvation. The results are discussed in the light of the recently discovered thiamic acid.