Effects of Estradiol on the Biosynthesis of Pyridine Nucleotide Coenzymes in the Rat Uterus1

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Abstract
The levels of NAD and NADP in the uterus of the ovariectomized mature rat increase after estradiol treatment. Incubation of uterine tissue slices in vitro with either 14C-nicotinamide or 14C-nicotinic acid and subsequent isolation of 14C-metabolites indicates that both precursors are incorporated into NAD. The labeling pattern of intermediates of NAD biosynthesis suggests that both the nicotinamide pathway and the nicotinic acid pathway for NAD synthesis are active in uterus. Nicotinic acid is incorporated into NAD at a rate that is 2.7 times that observed for nicotinamide when both are added in vitro at a concentration of 1.7 .times. 10-5 M. The incorporation of 14C-nicotinic acid into NAD in uteri from rats given estradiol for 5 h is increased, while the incorporation of 14C-nicotinamide into NAD is not increased by the hormone. A comparison of the uterine levels of intermediates in the nicotinic acid pathway for NAD synthesis between control and 4 h estradiol treated rats indicates that estradiol may cause a specific increase in the rate of conversion of deamido nicotinamide ribonucleotide to deamido-NAD to increase the overall flux of intermediates through this pathway.

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