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

PGF_2a has been proposed as a mediator of mammalian ovulation. To elucidate further the role of PGF_2a in the process of ovulation, PGF and PGF_2a metabolite were measured by radioimmunoassay in the perfusate of an 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 PGF_2a antisera a 40% cross reaction with PGF_1a, hence total PGF was measured with this antisera.] Both PGF and PGF_2a metabolite showed a linear increase with time and numbers of ovulations.PGF media accumulation was 575 pg/ovary/ovulation/hr and PGF_2a 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 total follicles. These data best fit a model of independent ovulatory units producing PFG_2a without recruitment or interaction between them. We infer the PGF and PGF_2a metabolites in this system can be used as a direct index of the ovulation process.