PGE receptor characteristics on porcine luteal cells during the estrous cycle and early pregnancy

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This study examined the affinities and concentrations of prostaglandin E (PGE) receptors on porcine luteal cells during the estrous cycle and early pregnancy. Corpora lutea (CL) were obtained from nonpregnant gilts at days 9 ( n = 4), 12 ( n = 3), and 14 ( n = 6); three gilts possessed red, vascular CL and three gilts had white nonvascular CL) of the estrous cycle, and days 9 ( n = 4), 12 ( n = 3), 14 ( n = 5), and 30 ( n = 5) of pregnancy. The CL were dissociated enzymatically to disperse single cells and the red blood cells were removed by elutriation. The luteal cells were assayed for specific PGE binding by displacement analysis with use of [ 3H] PGE 2 and varying concentrations of unlabeled PGE 2. The specific binding of [ 3H] PGE 2 to luteal cells decreased ( p < 0.05) from days 9 to 14 of the estrous cycle, but only decreased ( p < 0.05) from days 9 to 12 of pregnancy. Specific binding was higher ( p < 0.05) on day 14 of pregnancy than the comparable stage of the estrous cycle. The affinities of PGE receptors decreased ( p < 0.05) only on the luteal cells dissociated from red, vascular CL of day 14 nonpregnant gilts compared with those of other days of the estrous cycle and pregnancy. The number of PGE receptors on porcine luteal cells was similar ( p > 0.05) in pregnant and nonpregnant gilts, but decreased ( p < 0.05) on days 12–14 postestrus. During early pregnancy, it was evident that high affinity PGE receptors are sustained on porcine luteal cells; however, the role of the PGE receptors in maternal recognition of pregnancy remains speculative.