Estradiol-17 beta is produced in bovine corpus luteum

The aim of this study was to investigate the expression of cytochrome P450 aromatase (aromatase) mRNA, its activity, and estradiol-17 beta (estradiol) secretion in bovine corpus luteum (CL) during the estrous cycle. Expressio n of aromatase mRNA was examined in CL at the early, mid, late, and regress ed luteal stages by using a reverse transcription-polymerase chain reaction . Aromatase mRNA was detected in all luteal stages examined, although aroma tase expression was significantly lower during the early and regressed lute al phases compared to the mid and late luteal phases. Moreover, cultured mi dluteal cells clearly converted exogenous [H-3]androstenedione into estradi ol, and an aromatase inhibitor significantly inhibited this conversion. To characterize the local release of estradiol within the CL during the estrou s cycle, an in vitro microdialysis system (MDS) of CL was conducted. Estrad iol in MDS perfusate was confirmed by a reverse-phase high-performance liqu id chromatography in combination with enzyme immunoassays. Basal release of estradiol from microdialyzed CL did not change during the estrous cycle. A dditionally, when freshly prepared midluteal cells were exposed to estradio l (10(-14) to 10(-9) M), estradiol stimulated prostaglandin (PG) F-2 alpha secretion (P < 0.05), although it did not affect progesterone and oxytocin secretion. The overall results indicate that estradiol is produced locally in bovine CL throughout the estrous cycle, and they suggest that estradiol plays a role in regulating PGF(2 alpha) production in CL as an autocrine/pa racrine factor.