Characterization of messenger ribonucleic acid expression for prostaglandin F2 alpha and luteinizing hormone receptors in various bovine luteal cell types.

LH and prostaglandin F2 alpha (PGF2 alpha) control the life span and function of the corpus luteum (CL). Nevertheless, identification of the various cell types (steroidogenic and nonsteroidogenic) expressing the receptors for these hormones remains controversial. In this study we characterized LH and PGF2 alpha receptor (r) expression in the various luteal cell types using quantitative reverse transcription-polymerase chain reaction. We found, in agreement with previously described functions of PGF2 alpha, that the two steroidogenic cell types, as well as luteal endothelial cells, expressed PGFr. In contrast, LHr was mainly expressed by small luteal cells. A similar pattern of PGFr and LHr expression was observed in steroidogenic cells luteinized in vitro and in cells derived from the mature CL. The expression of these two receptors was inversely affected by increased levels of cAMP (achieved by incubating cells with varying doses of forskolin); LHr expression was down-regulated by 50% in the presence of 10 microM forskolin (p < 0.05), while an increase was observed in PGFr expression. In granulosa-derived luteal cells, maximal expression of PGFr was higher (approximately by 3-fold, p < 0.05) than in the theca-derived luteal cells. PGF2 alpha, mimicking its in vivo effect, markedly down-regulated LHr expression in thecaderived luteal cells, abolishing expression at a concentration of 100 ng/ml. In summary, these studies depict cAMP and PGF2 alpha as major regulators of PGFr and LHr expression in the two steroidogenic cell types. All three major cell types of the CL (steroidogenic and endothelial) express PGFr. LHr mRNA, on the other hand, was detected mainly in small luteal cells. Such broad cellular distribution of PGFr may highlight the significant role played by this prostaglandin in the bovine CL.