Estradiol-mediated suppression of apoptosis in the rabbit corpus luteum is associated with a shift in expression of bcl-2 family members favoring cellular survival. Biol Reprod 59: 820–827

In the rabbit, estradiol is the primary luteotropic hormone. Estradiol withdrawal results in a rapid decline in serum proges-terone and eventually in corpus luteum (CL) regression. The ob-jective of this study was to determine whether estradiol modu-lates luteal cell apoptosis. In the first experiment, rabbits were randomly assigned to one of five experimental groups. An empty capsule (control) or estradiol-filled Silastic capsule was inserted s.c. on Day 0 of pseudopregnancy (day of hCG administration). On Day 11 of pseudopregnancy, some of the group I (control) and group II (estradiol capsule) rabbits were subjected to lapa-rotomy, and one ovary from each rabbit was perfused in vitro to determine progesterone secretion rates. The CL from the con-tralateral ovary were dissected, snap-frozen, and stored at 2708C until analyzed for internucleosomal DNA cleavag