[Niacin deficiency and correlation between oxidative reactions of the pentose phosphate pathway of carbohydrate metabolism and transketolase activity].

Rat were kept on the niacine-deficient diet with addition of excess L-leucine. This led to an appreciable reduction of the level of all the forms of nicotinamide coenzymes in the liver, heart, brain and blood, as well as to the loss of niacine function (as coenzyme) in dehydrogenase reactions in the test tissues. The increase in the glucose-6-phosphate level in the heart dependent on changes in the activity of glucose-6-phosphate dehydrogenase. The keeping on the diet devoid of niacine was followed by activation of blood transketolase and by transition of the biosynthesis of pentosophosphates from the oxidative to the non-oxidative branch of the pentosophosphate pathway. Administration of 3-acetylpyridine to both intact and avitaminotic rats revealed vitamin action of the preparation on the level of nicotinamide coenzymes and the activity of NADP-dependent dehydrogenase and showed that 3-acetylpyridine is not fit as antivitamin for use with a purpose of aggravating niacine deficiency in rats under the experimental conditions described.