Effect of hyperthyroidism on liver pyridine nucleotide synthesis.

The concentration of pyridine nucleotides in the liver of the hyperthyroid rat is low (14). Whether this is a result of decreased synthesis, increased destruction, or both, is not known. Several groups of investigators have shown that when the normal rat or the normal mouse is given a single dose of nicotinamide the concentration of pyridine nucleotides in the liver rises rapidly for a few hours and then falls to within the normal range within 24 hours (5-7). This procedure which should give a measure of the capacity of the rat to synthesize liver pyridine nucleotides, has been used in the present investigation to study the rate and extent of synthesis of pyridine nucleotides in the liver of the hyperthyroid rat, the hyperthyroid mouse and the rat treated with 2,4-dinitrophenol.