The effects of peritoneal macrophages on monolayered luteal cell progestin secretion in the rat

Functionally active or regressing luteal cells were obtained from pseudo-pregnant (psp) rats between days 5-8 of psp or on day 15 of psp, respectively. They were monolayer-cultured (10(6)/dish) in the presence of 0.2 micrograms/ml LH 2.0 micrograms/ml PRL and 10 micrograms/ml pregnenolone for 4 days with or without macrophages, although functionally active luteal cells secreted progesterone dominantly during day 1 of culture (Day 1), the amounts of progesterone and 20 alpha-OH-P secreted were inverted on Day 2, and the dominance of 20 alpha-OH-P continued from Day 2 to Day 4. In the functionally regressing luteal cell culture, more 20 alpha-OH-P than progesterone was secreted throughout the culture period. The addition of peritoneal macrophages (2.5 X 10(6] to the active luteal cell monolayer lengthened the dominance of progesterone secretion for an additional day and the inversion occurred on Day 3. The progestin ratio (progesterone/20 alpha-OH-P) on Day 2 was maintained significantly higher. The daily addition of macrophages maintained the progesterone dominance throughout the culture period. On the other hand, macrophages had no effect on luteal cells already functionally regressing. These results indicate that macrophages are effective in maintaining the progesterone secreting activity of luteal cells in vitro.