Characterization of ovarian carbonyl reductase gene expression during ovulation in the gonadotropin-primed immature rat

In this differential-display polymerase chain reaction-based study, four di fferent primer sets generated cDNA fragments of ovarian carbonyl reductase genes that were uniquely expressed during the ovulatory process in eCG-prim ed immature rats, The temporal pattern of expression of this aldo-keto redu ctase gene was delineated by extracting ovarian RNA at 0, 2, 4, 8, 12, and 24 h after induction of ovulation via injection of the primed animals with hCG, The results showed that at least four homologous forms of this gene we re transcribed during ovulation. Northern blot analyses indicated a 14-fold increase in ovarian mRNA for carbonyl reductase, with expression reaching a peak at 8 h after hCG treatment and then declining to negligible levels d uring the next 16 h. In situ hybridization revealed that mast of the transc ription was in the thecal connective tissue of the ovary and was absent fro m the granulosa layer of ovarian follicles. Treatment of the animals with o vulation-blocking doses of epostane (an inhibitor of progesterone synthesis ) or indomethacin (an inhibitor of prostanoid synthesis) did not reduce the expression of ovarian carbonyl reductase. Nevertheless, the temporal patte rn of expression of carbonyl reductase after the induction of ovulation sug gests that this enzyme activity is at Least indirectly associated with the ovulatory process.