Effects of B-Vitamin Deficiencies and of Starvation on Liver Enzyme Activities of Growing Rats

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Abstract
The feasibility of using enzyme assays to evaluate a specific vitamin deficiency in the presence of multiple vitamin deficiencies was investigated in a series of studies in which rats were fed complete, B-vitamin free, pyridoxine-deficient or thiamine-deficient diets. The activities of alanine and aspartate aminotransferase, serine dehydratase, and the pentose phosphate-metabolizing system were measured in liver homogenates. In a simple pyridoxine or thiamine deficiency, the activities of enzymes requiring these vitamins as co-factors were significantly lowered. The pentose phosphate-metabolizing system was also depressed in a multiple B-vitamin deficiency. The response of the pyridoxine-dependent enzymes to a thiamine deficiency and to a B-vitamin free diet was similar. The activities of serine dehydrates and alanine aminotransferase were increased, whereas aspartate amino transferase activity was somewhat decreased. With the exception of aspartate aminotransferase, the response of the liver enzymes to fasting and to the vitamin-free diet was also similar. It was concluded that measurements of the pentose phosphate-metabolizing system can possibly be used to evaluate a thiamine deficiency in malnutrition. However, the pyridoxine-dependent enzymes cannot reliably be used to predict a pyridoxine deficiency when other B-vitamins are limiting in the diet because these enzymes are sensitive to changes in food intake and to other B-vitamin deficiencies.