Prostaglandin F2a, an ovulatory intermediate in the in vitro perfused rabbit ovary model

PGF2a has been proposed as a mediator of mammalian ovulation. To elucidate further the role of PGF2a in the process of ovulation, PGF and PGF2a metabolite were measured by radioimmunoassay in the perfusate of an in vitro perfused rabbit ovary preparation. Perfusion medium samples were collected over a 10 to 12 hour period from ovaries perfused with tissue culture M199 (total volume 150 ml, sample volume 3 ml) to which varying amounts of hCG had been added. [The PGF2a antisera a 40% cross reaction with PGF1a, hence total PGF was measured with this antisera.] Both PGF and PGF2a metabolite showed a linear increase with time and numbers of ovulations. PGF media accumulation was 575 pg/ovary/ovulation/hr and PGF2a metabolite accumulation was 367 pg/ovary/ovulation/hr. Medium prostaglandin content could be correlated with numbers of ovulations, ovulatory efficiency (number of ovulations/total follicles) but not total follicles. These data best fit a model of independent ovulatory units producing PGF2a without recruitment or interaction between them. We infer that PGF and PGF2a metabolites in this system can be used as a direct index of the ovulation process.