Uterine blood flow during early pregnancy in ewes: interaction between the conceptus and the ovary bearing the corpus luteum.

To determine if a transient increase in uterine blood flow (BF) and estradiol-17 beta (E2 beta) 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 an 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 E2 beta and progesterone (P4) in UA and E2 beta in UV and UF were determined by radioimmunoassay. For NP ewes, BF (ml/min) was not different for UH ipsilateral or contralateral to the ovary bearing the corpus luteum (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 less than .01) twofold (13.3 +/- .9).(ABSTRACT TRUNCATED AT 250 WORDS)