GONADOTROPIC AND LOCAL-CONTROL OF THE DEVELOPING CORPUS-LUTEUM IN RHESUS-MONKEYS

The actions of the mid-cycle gonadotrophin surge to convert the pre-ov ulatory follicle into the corpus luteum are not well understood in pri mate species. In experiments titrating the surge duration required in macaque monkeys during in-vitro fertilization (IVF)-related cycles, sh ort (less-than-or-equal-to 14 h) LH surges similar to those in rodents and domestic animals failed to initiate peri-ovulatory events. Attenu ated (24 h) surges, one-half the duration of spontaneous surges in pri mates, re-initiated oocyte meiosis and initial luteinization of granul osa cells. However, only surges of greater-than-or-equal-to 48 h susta ined luteal development and function to produce luteal phases of appro ximately 13 days. Three approaches-immunocytochemistry of steroid rece ptors, binding of radiolabelled steroid, and reverse transcription-pol ymerase chain reaction of mRNA-indicate that progesterone receptor (PR ), but not oestrogen receptor, is expressed in the macaque corpus lute um. Studies on cells collected before and after the gonadotrophin surg e identified a novel action of LH to induce PR expression in luteinizi ng granulosa cells. Thus, the LH surge requirements vary between non-p rimate and primate species, as well as between peri-ovulatory events, and the LH surge may promote cellular recognition of paracrine and aut ocrine factors (e.g. progesterone) that become predominant in the deve loping corpus luteum.