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Effect of Dexamethasone on Follicular Development
L. Christie Rockwell, Ph.D.
School of Medicine, University of Maryland, Baltimore
Follicular development is necessary for normal ovulation and reproductive function. Abnormal follicular maturation or atresia can cause fertility problems. Atresia is an apoptotic process that normally reduces the number of medium to large size follicles. Two families of intracellular proteins (Bcl-2 and Iaps) mediate apoptosis in ovarian follicles. When dexamethasone was administered during the PMSG/hCG priming regimen to immature rats the result was an increase in ovulations and litter size compared with controls. Because dexamethasone regulates both Bcl- 2 proteins and IAPs in other cells and tissues (Lotem and Sachs, 1995; Wen et al., 1997; Yomomoto et al., 1998) we surmise that these particular intracellular proteins, mediators of apoptosis in the follicle, may be the key to deciphering how glucocorticoids effect follicular development. We hypothesize that the effect of dexamethasone in the ovary is to suppress atresia in antral follicles and thus increase the number of follicles that ovulate in response to hCG (endogenous analog for LH). The project will evaluate whether dexamethasone alters follicular development during the priming/treatment period such that a larger crop of follicles ovulate.
Two series of studies will be conducted. The first will evaluate the number of healthy versus atretic ovarian follicles, at 5 stages of follicular growth, at 4 time points following either gonadotropin priming (controls) or gonadotropin priming in combination with dexamethasone treatment (DEX treated) of animals. In a second series of studies we will harvest ovarian tissue from which to extract total RNA to assay mRNA expression of Bcl-2 genes from control and DEX treated animals. If dexamethasone treatment alters Bcl-2 mRNA expression in the rat ovary, we will examine protein expression using western blot analysis. Future studies will similarly evaluate the effect of dexamethasone on IAPs in the rat ovary.
