Niacin and Anti-Niacin Activity of 3-Acetylpyridine in Dogs

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Abstract
3-AP has been shown to have both niacin and anti-niacin activity. It is about 1/6 as active as NA in increasing urinary excretion of NMN in normal dogs fed a stock diet. Twenty-five to 260 mg of 3-AP daily protected dogs against blacktongue over long periods. Daily doses of 25 to 60 mg of 3-AP were sufficient to cure blacktongue. Niacin-deficient dogs appeared to have a diminished capacity to convert 3-AP to niacin as shown by urinary NMN excretion studies and by the fact that doses of 25 to 260 mg of 3-AP were highly toxic in deficient dogs but relatively well tolerated by normal dogs. NA prevented 3-AP toxicity but was ineffective once the toxic syndrome had developed. The data suggest that animals have a limited capacity to transform 3-AP to niacin. When the dosage of 3-AP exceeds this capacity, the 3-AP molecule acts as a specific antagonist to niacin.