Biology of Reproduction, Vol 14, 579-585, Copyright © 1976 by Society for the Study of Reproduction

Plasma Levels of Estradiol and Progesterone in the Cat During Polyestrus, Pregnancy and Pseudopregnancy

¹ Department of Reproductive Physiology, Oregon Regional Primate Research Center, Beaverton, Oregon 97005

The levels of estradiol and progesterone in the systemic plasma of four domestic cats during pregnancy, pseudopregnancy and polyestrus were determined by radioimmunoassay. During polyestrus, estradiol values fluctuated between peaks (59.5 ± 13.4 (SD) pg/ml; n = 13) and troughs (8.1 ± 3.8 (SD) pg/ml; n=12) with an interpeak period of 15.8 ± 3.8 days (n=9). After the animals had been mated to either intact or vasectomized males, their estradiol levels declined sharply from peak values and remained low (6-12 pg/ml) during pseudopregnancy and pregnancy except for a slight rise just before parturition. Essentially no progesterone could be detected during polyestrus and for 2 to 3 days after copulation with either intact or vasectomized males, but by Day 21 of pregnancy or pseudopregnancy progesterone rose to a peak of either 35 or 24 ng/ml respectively. After Day 21 of pregnancy, progesterone gradually declined to 10 ng/ml by Day 60, 5 ng/ml just before parturition, and <1 ng/ml just after parturition. After Day 21 of pseudopregnancy, progesterone levels declined rapidly to 4 ng/ml by Day 40, 2 ng/ml by Day 50 and <1 ng/ml by Day 63-65. Estrone was measured throughout pregnancy, pseudopregnancy and polyestrus in one animals; no major elevations were detected.

Note:
ACKNOWLEDGMENTS The authors wish to thank Pamela Holt for her excellent technical assistance and Bernie Humberg for the typing of the manuscript. This is publication no. 848 of the Oregon Regional Primate Research Center. This investigation was supported by General Research Support Grant RR5694 from the General Research Support Branch, and Grant RR00163, Grant for the Operation of the Oregon Regional Primate Research Center, from the Animal Resources Branch, Division of Research Resources, National Institutes of Health, as well as Program Project Grant HD05969 from the Center for Population Research, National Institute of Child Health and Human Development, National Institutes of Health.

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