Dominant Bovine Ovarian Follicular Cysts Express Increased Levels of Messenger RNAs for Luteinizing Hormone Receptor and 3β-Hydroxysteroid Dehydrogenase Δ4,Δ5 Isomerase Compared to Normal Dominant Follicles

Abstract

The objective was to compare ovarian steroids and expression of mRNAs encoding cytochrome P450 side-chain cleavage, cytochrome P450 17 alpha-hydroxylase, cytochrome P450 aromatase, 3 beta-hydroxysteroid dehydrogenase Delta(4),Delta(5) isomerase, LH, and FSH receptors and estrogen receptor-beta in ovaries of cows with dominant and nondominant ovarian follicular cysts and in normal dominant follicles. Estradiol-17 beta, progesterone, and androstenedione concentrations were determined in follicular fluid using specific RIAs. Dominant cysts were larger than young cysts or dominant follicles, whereas nondominant cysts were intermediate. Estradiol-17 beta (ng/ml) and total steroids (ng/follicle) were higher in dominant cysts than in dominant follicles. Expression of LH receptor and 3 beta-hydroxysteroid dehydrogenase mRNAs was higher in granulosa cells of dominant cysts than in dominant follicles. Nondominant cysts had higher follicular concentrations of progesterone, lower estradiol-17 beta concentrations, and lower expression of steroidogenic enzyme, gonadotropin receptor, and estrogen receptor-beta mRNAs than other groups. In summary, increased expression of LH receptor and 3 beta-hydroxysteroid dehydrogenase mRNAs in granulosa and increased follicular estradiol-17 beta concentrations were associated with dominant cysts compared to dominant follicles. Study of cysts at known developmental stages is useful in identifying alterations in follicular steroidogenesis.

Aetiology and pathogenesis of cystic ovarian follicles in dairy cattle: a review

“…Therefore, alterations in ER-β expression may be involved in the development of COF. However, this hypothesis is not supported by data from Calder et al [80] showing that ER-β mRNA expression was not altered in growing young cysts. Odore et al [79] did, however, find decreased oestrogen receptor concentrations in follicular cysts, but the oestrogen receptor type was not defined.…”

“…Discrepancies between studies may be explained by differences in methodology such as demonstration of the receptor itself or its mRNA, and the division of cysts into oestrogenactive and oestrogen-inactive. In the same study, Calder et al [80] also studied developing "young cysts" but no differences in FSH/LH receptor mRNA were observed when compared to dominant follicles. Young cysts were, however, studied in the presence of existing cysts, i.e.…”

“…The LH surge initiates a complex multi-gene, multistep process in which timing is essential, finally leading to ovulation of the pre-ovulatory follicle [77]. According to Kawate et al [78], FSH and LH receptor numbers in granulosa cells of cysts are decreased when compared to normal follicles, but this is contradicted by data from Odore et al [79] and Calder et al [80]. Discrepancies between studies may be explained by differences in methodology such as demonstration of the receptor itself or its mRNA, and the division of cysts into oestrogenactive and oestrogen-inactive.…”

“…After all, the dominant follicle has to elicit an LH surge at the right time in its development by producing sufficient oestradiol. Oestrogen-active cysts show a higher expression of 3β-hydroxysteroid dehydrogenase mRNA, a steroidogenic enzyme [80], and cows developing a cyst have increased oestradiol concentrations during the early stages of follicular dominance [86]. However, Calder et al [80] were unable to observe changes in mRNA expression of steroidogenic enzymes in the follicle wall of young growing cysts.…”

“…Oestrogen-active cysts show a higher expression of 3β-hydroxysteroid dehydrogenase mRNA, a steroidogenic enzyme [80], and cows developing a cyst have increased oestradiol concentrations during the early stages of follicular dominance [86]. However, Calder et al [80] were unable to observe changes in mRNA expression of steroidogenic enzymes in the follicle wall of young growing cysts. They concluded that alterations of the endocrine system precede, and perhaps cause, the observed follicular alterations in cysts.…”