The influence of PRL, LH alone and in combination upon progesterone secretion by porcine luteal cells in aggregate culture.

Corpora lutea removed from ovarian of cycling pigs in early luteal phase (1-3 days) were used. After enzyme dispersion the luteal cells were suspended in medium M 199 supplemented with 10% of calf serum. Cultures were carried out in triplicate and incubated at 37 degrees C for 24 h. After that time the following hormones were added to the culture medium; 100 ng LH, or 100 ng PRL or 100 ng LH plus 100 ng PRL. The cells were incubated with hormone for 6, 12, 24 and 48 h. LH added to the medium resulted in the increase of progesterone secretion (P less than 0.05) only during 6 h incubation (140% of control progesterone). Stimulatory effect of PRL was observed only after 12 h incubation (300% of control progesterone; P less than 0.001). The addition of LH plus PRL decreased progesterone secretion after 6 h incubation (33.3% of control progesterone; P less than 0.05), a little stimulatory effect being observed after 24 h incubation (141% of control progesterone). This study confirmed the results obtained with monolayer cultures previously described. PRL appeared to be a luteotrophic hormone which is responsible for the increase of progesterone secretion by the early developing corpus luteum of pig. From these data it was concluded that luteal cells may require either LH or prolactin but not both at a time to sustain higher level of progesterone secretion.