Gonadotrophic and local control of the developing corpus luteum in rhesus monkeys

The actions of the mid-cycle gonadotrophin surge to convert the pre-ovulatory follicle into the corpus luteum are not well understood in primate species. In experiments titrating the surge duration required in macaque monkeys during artificial in-vitro fertilization (TVF)-related cycles, short (≤14 h) LH surges similar to those in rodents and domestic animals failed to initiate peri-ovulatory events. Attenuated (24 h) surges, one-half the duration ofspontaneous surges in primates, reinitiated oocyte meiosisand initial luteinization of granulosa cells. However, only surges of ≥48h sustained luteal development and functionto produce luteal phases of ∼ 13 days. Three approaches—immunocytochemistry of steroid receptors, binding of radiolabelled steroid, and reverse transcription-polymerase chainreaction of mRNA—indicate that progesterone receptor (PR), but not oestrogen receptor, is expressed in the macaque corpus luteum. Studies on cells collected before and after the gonadotrophin surge identified a novel action of LH to induce PR expression in luteinizing granulosa cells. Thus, the LH surge requirements vary between non-primate and primate species, as well as between peri-ovulatory events, and the LH surge may promote cellular recognition of paracrine and autocrine factors (e.g. progesterone) that become predominant in the developing corpus luteum.