[Removal of nicotinic acid 7-14C from the body of rats on a varying supply of vitamin PP].

Dynamic was studied for nicotinic acid (NA-7-14C) and its total metabolites excretion with area of animals under different physiological states (standard PP-avitaminosis). Various "efficiency" is shown for systems regulating homeostasis of this vitamin. When it is administered both in the amount close to the physiological dose (50 mg per 1 kg of weight) and exceeding the dose (500 mg per 1 kg of weight). The data obtained make it possible to draw a conclusion that the biological halflife period of Na-7-14C administered in excess of a physiological dose depends mainly on the rate of the unchanged vitamin PP excretion with urea and when it is administered in the physiological amount the period depends on the rate of the acid-metabolic transformations in the organism.