Effect of thyrotropin on thyroid pyridine nucleotides in vitro.

Abstract

Thyrotropin, 3 or 50 mU, given iv to thyroid hormone-treated, 125I-injected mice, greatly increased blood radioactivity measured 3 and 9 hr later but thyroid pyridine nucleotide concentrations were unchanged. Administration of 400 mU thyrotropin caused a marginal increase in NADP in one of 2 experiments; 9 hr after injection of a potent LATS preparation, thyroid pyridine nucleotide levels were unaltered. Injection of 3 or 4 U thyrotropin into 2 strains of rat resulted in an increase in thyroid NADP; NADPH and total NADP concentrations were unchanged. These changes were reflected in an increased NADP/NADPH ratio in the thyrotropin-treated groups and are consistent with the hypothesis that thyrotropin primarily increases NADPH oxidation. In mice and rats fed a lowiodine diet the concentration of all pyridine nucleotides except that of NADPH was increased; in rats the NAD/NADH ratio was elevated. In rats addition of PTU to the diet caused a further increase in the concentration of NADP and also an elevation ...