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University of Wisconsin, Madison 53706
Abstract
Blood was collected from the right and left main uterine veins, right and left main ovarian veins and jugular vein of mares. Progesterone concentration was determined by radioimmunoassay in the five plasma samples for each of 22 mares which were killed on days 24, 30,40, 50, 60, 80, 100, 160 or 220 of pregnancy. The mares were grouped on the basis of the location of the secondary corpora lutea (2°CL) relative to the primary corpus luteum (1°CL). The 1°CL secreted progesterone into the ovarian vein at least until day 80. The 2°CL produced considerable progesterone as indicated by high levels of progesterone in the ovarian venous effluent from ovaries which contained only 2°CL. Ovaries which did not contain CL (1°CL or 2°CL) did not secrete progesterone (no significant difference between ovarian veins and jugular vein). All 22 mares had high levels of progesterone in venous effluent from ovaries which contained luteal structures except the one mare which was killed on day 220. The placenta or uterus contributed to the concentration of progesterone in the systemic circulation by day 80 of pregnancy and continued to secrete progesterone until day 220, which was the last day studied.
1 From the Department of Veterinary Science, University of Wisconsin, Madison, Wisconsin 53706. Supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison and Grant No. 630-0505A from the Ford Foundation and by Public Health Service Training Grant No. 5-T01-HD-00104-08.
2 The authors wish to express their appreciation to Dr. L. Nuti, Dr. B. C. Wentworth and Miss L. Schuler for assistance in progesterone determination; to Mr. W. Steffenhagen for figure preparation; to Mr. R. Elderbrook and Mr. R. Douglas for assistance in collection of blood and to Mr. A. Hardie for assistance in statistical analyses of the data.
3 Trainee of the Endocrinology-Reproductive Physiology Program, University of Wisconsin, Madison. Present address: Department of Animal Sciences, University of New Hampshire, Durham 03824.
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