Parthenogenetic activation induced by progesterone in cultured mouse oocytes

Progesterone induced in vitro parthenogenetic activation of ovulated mouse oocytes. Progesterone (100 μM, 31.4 μg/ml) induced a high rate (90%) of activation and progression of the second meiotic division from metaphase to anaphase/telophase and pronuclear formation. Oocytes degenerated at progesterone concentrations of 150 μM and above, whereas 50 μM concentrations or less induced quite little or no activation. Aging of the oocytes prior to treatment and a longer treatment period had significant effects on activation. Oocytes treated with 100 μM progesterone at 16, 18, 20, or 22 h after hCG injection for 6 h showed 50, 85, 89 and 98% activation, respectively, while the effect on activation was less significant when these oocytes were treated for 2 or 4 h. Few oocytes (0-4%) were activated in controls that were incubated in the presence of solvent (0.5% DMSO) only. The presence of cumulus cells did not exert significant effects on the incidence of activation by progesterone. Other steroids tested were cholesteryl sodium sulfate, pregnenolone, 17α-hydroxy-20β-dihydroprogesterone, 17α-hydroxyprogesterone, 20α-hydroxy-progesterone, 20β-hydroxyprogesterone, androstenedione, testosterone, and estradiol-17β. Both 20α-hydroxyprogesterone and 20β-hydroxyprogesterone induced activation, but the remainder induced low or no activation. When culture was continued after progesterone exposure, 60% of oocytes developed to the 2-cell stage, and a small proportion (3%) developed to the blastocyst stage. These results show that when progesterone and its metabolites are present at high concentrations (100 μM) for a long period (6 h), they have the unique property of inducing in vitro parthenogenetic activation in mouse oocytes.