Uterine Blood Flow during Early Pregnancy in Ewes: Interaction between the Conceptus and the Ovary Bearing the Corpus Luteum

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Abstract
To determine if a transient increase in uterine blood flow (BF) and estradiol-17β(E2β) secretion occurs during maternal recognition of pregnancy in ewes (as previously observed for sows and cows), 40 nonpregnant (NP) ewes were assigned in equal numbers to surgery on d 9, 11, 13 or 15 postestrus (d 0 = day of estrus). For 20 NP ewes (five/day), each uterine horn (UH) was flushed with saline and uterine flushings (UF) collected. For the remaining 20 ewes, BF was determined for each UH using electromagnetic transducers, and samples of uterine arterial (UA) and uterine venous (UV) blood were obtained from each UH. After art intervening cycle, each ewe was mated, subjected to surgery on the same day postmating as during her previous nonmated cycle, and BF measurements and UA and UV samples were obtained. In addition, each UH of pregnant (P) ewes was flushed and the location of conceptuses was determined. Concentrations of E2β and progesterone (P4) in UA and E2β in UV and UF were determined by radioimmuno assay. For NP ewes, BF (ml/min) was not different for UH ipsilateral or contralateral to the ovary bearing the corpus lteum (CL), and did not differ across days, averaging 6.5 ± .4. For P ewes, BF to UH contralateral to the ovary bearing the CL on all days and BF to UH ipsilateral to ovaries bearing CL on d 9 was similar to BF of either UH of NP ewes, averaging 6.8 ± .6. On d 11, 13 and 15 of pregnancy, BF to UH ipsilateral to the ovary bearing CL was elevated (P<.01) twofold (13.3 ± .9). Concentrations of E2β were not different in UA or UV blood or between NP and P ewes. Content of E2β in UF of P ewes, however, was greater (P<.05) than for NP ewes (35.2 ± 2.1 vs 16.7 ± 2.4 pg/UH). The possibility that this is an estrogen induced increase in uterine BF and a possible role for increased uterine BF during early pregnancy are discussed. Copyright © 1984. American Society of Animal Science . Copyright 1984 by American Society of Animal Science.

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