DIFFERENTIAL-EFFECTS OF LH AND PGE(2) ON PROGESTERONE SECRETION BY SMALL AND LARGE PORCINE LUTEAL CELLS

This study examined the effects of LH and PGE(2) on progesterone secre tion by small and large porcine luteal cells with or without low-densi ty lipoproteins. Corpora lutea were isolated from gilts 13-14 days aft er administering gonadotrophins; enzymatically dissociated and small a nd large cells were isolated by elutriation. Culture plates, 24-well, were then seeded with 150 000 small or 30 000 large luteal cells suspe nded in 1 ml M199 medium supplemented with 5 mu g insulin ml(-1), 40 n g hydrocortisone ml(-1) and with or without low-density lipoproteins ( 50 mu g cholesterol ml(-1)) or PGE(2). Cells were cultured for up to 2 4 h in a humidified incubator at 37 degrees C under 5% CO2 in air. The low-density lipoproteins stimulated (P < 0.05) progesterone secretion by large, but not small, luteal cells. Prostaglandin E(2) stimulated (P < 0.05) progesterone production by large luteal cells in a dose-dep endent manner, and the stimulatory effects of PGE(2) were greater (P < 0.05) in the presence than in the absence of low-density lipoproteins . Progesterone secretion by small luteal cells was not significantly a ffected by PGE(2). Progesterone production by small luteal cells was e nhanced (P < 0.05) by LH, and the stimulatory effects of LH were great er (P < 0.05) in the presence than in the absence of low-density lipop roteins. In the absence of these lipoproteins, LH had no effect on pro gesterone secretion by large luteal cells; however, in the presence of low-density lipoproteins, LH increased (P < 0.05) progesterone secret ion by large cells, though to a lesser (P < 0.05) extent than the effe ct of LH on small cells. These data demonstrate that progesterone secr etion by porcine luteal cells is stimulated differentially by LH and P GE(2) and that small luteal cells are more responsive to LH and PGE(2) acts primarily on large luteal cells.