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Intrauterine Oxygen Tension in the Rat During Progestation: Its Possible Relation to Carbohydrate Metabolism and the Regulation of Nidation

Department of Comparative Biochemistry and Physiology, University of Kansas Lawrence, Kansas 66044

This research was supported in part by funds from the Lalor Foundation (1966) and a University of Kansas Biomedical Research Grant (1967).

Abstract

Intrauterine oxygen tension was measured in vivo in the adult rat throughout pseudopregnancy and during the first 6 days of pregnancy. Average pO₂ increased from 22 mm Hg during Day O (estrus) to between 35 and 40 mm Hg during Days 1–4 of the luteal phase. No significant differences were measured between pseudopregnant and pregnant rats. Between Days 4 and 5, a significant increase in pO₂ was measured in nondecidualizing uteri of pseudopregnant or unilaterally pregnant rats. Oxygen tension was measured at 59 mm Hg by Day 7 of pseudopregnancy, after which a gradual decline to 37 mm Hg on Day 12 was measured. In contrast, pO₂ in decidualized cornua did not change significantly during Days 4–5 of progestation or during Days 4–9 of pseudopregnancy. The present evidence, correlated with studies of uterine respiration, indicated an inverse relation between intrauterine pO₂ and oxygen consumption, suggesting that during the pre-implantation period, the conceptus and the uterus may compete for available oxygen. Changes in pO₂ during the time of implantation (Days 4–5) indicated that a major site for oxygen diffusion is the dense subepithelial capillary bed on the lateral surfaces of the antimesometrial side of the uterus. Such localization of a source of oxygen may provide a specificity to the site of nidation or decidualization (but not its timing) in pregnant rats. A correlation of changes in intrauterine oxygen tension with carbohydrate metabolism in the endometrium revealed a possible means by which ovarian steroid hormones, through their action on intrauterine pO₂, may adjust cell metabolism and thus regulate the timing and magnitude of sensitivity to decidualization and the process of nidation in the rat. Such control may be, in part, by means of regulation of the availability of substrate to the endometrium and blastocyst. (Endocrinology 83: 706,1968)

Footnotes

¹ Research Assistant, 1966–67; The National Science Foundation Summer Graduate Traineeship Program (1967).

Received January 12, 1968.

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