Hormonal Control of Pyridine Nucleotide Activity in the Uterus: A Model for Progestational Differentiation1

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Abstract
To evaluate the roles of estrogen and progesterone in regulating NADP content in endometrium during progestation, adult rats were ovariectomized on day 0 of pseudopregnancy. Using a radiometric enzymatic recycling assay, daily measurements of NADP+ and NADPH were made in 5 experiments [exp.]: ovariectomized controls; replacement with 1.0 .mu.g estrone[E]/day or 2.0 mg progesterone[P]/day; a combination of 1.0 .mu.g E + 2.0 mg P (Exp. A); and 0.5 .mu.g estrone + 1.0 mg P on day 0 followed by the regimen of Exp. A thereafter (Exp. B). Following ovariectomy, the content of NADP declined but the concentration stabilized at a level equivalent to that measured during proestrus (18-21 pmol/mg). Daily treatment with E generated a bimodal pattern with peaks on days 2 and 5 (30-32 pmol/mg) treatment with P induced peaks on days 3 and 6 (40-67 pmol/mg). An increase in the NADP+/NADPH ratio, measured on day 1 in ovariectomized rats, was blocked by E until day 3, but was not affected by P. Addition of E to the P regimen (Exp. A) stimulated an increase in tissue mass without a concomitant increase in P-maintained NADP content and without altering the P-maintained pattern. Slight alterations in the steroid hormone regimen on day 0 (Exp. B) significantly altered the subsequent patterns of NADP content and concentration on days 3-4 to mimic the transient peak in activity measured at this time in intact pseudopregnant rats. Apparently, at the dosages of hormones used (limited by physiological constraints), the production of high concentrations of NADP during early progestation is a P-dependent phenomenon, modulated by E. A relationship of these hormone-dependent changes to key facets of progestational differentiation dependent on pyridine nucleotide metabolism is presented.
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