Isolation of differentially expressed aldose reductase in ovaries after estrogen withdrawal from hypophysectomized diethylstilbestrol treated rats: increased expression during apoptosis.

More than 99% of the follicles are eliminated by apoptosis before reaching ovulation. Several growth factors and hormones inhibit apoptosis in the ovary, including estrogen. Using differential display of mRNA, aldose reductase was shown to increase in the ovary of diethylstilbestrol treated hypophysectomized rats after estrogen withdrawal, inducing apoptosis. The aldose reductase mRNA expression was confirmed to be 2.2 +/- 0.2-fold higher after estrogen withdrawal using northern blot analysis. In addition, untreated immature rats showed a 1.7 +/- 0.3-fold higher expression of ovarian aldose reductase mRNA compared to ovaries 24 h after pregnant mare's serum gonadotropin treatment, decreasing apoptosis in the ovary. In the prostate, the level of aldose reductase was increased 3.1 +/- 1.1-fold 2 days after castration induced apoptosis. Although the physiological role of aldose reductase in the ovary is not known, these data suggest that aldose reductase may be part of a hormonally regulated apoptotic pathway in the ovary and prostate.