Abstract— It is shown that transketolase activities in red blood cells and whole brain of normal and thiamine‐deficient rats correlate well with heart frequencies. The effect of thiamine depletion on the levels of acetylcoenzyme A (acetyl‐CoA) and acetylcholine (ACh), and on the activities of pyruvate dehydrogenase, choline acetyl‐transferase and acetylcholine esterase was studied in whole brains of thiamine‐deficient, thiamine‐supplemented ad libitum and pair‐fed rats. The concentrations of acetyl‐CoA and ACh decreased in thiamine‐deficient brains by 42 and 35 per cent, respectively. Total pyruvate dehydrogenase activity did not change during vitamin B1 deficiency. The ‘resolved’ enzyme, reconstituted with thiamine diphosphate, had an association constant of 5.4 × 10−6m. Choline acetyltransferase and acetylcholine esterase activities remained unchanged in thiamine deficiency. Possible mechanisms which could explain the reduced Ach levels in vitamin B1 deficiency are discussed.

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