Expression of proopiomelanocortin-related peptides in human follicular fluid

In order to evaluate the expression of the opioid precursor proopiomelanocortin (POMC) in the ovarian follicle, we measured 6 of its main end-products in 23 follicular fluids. We coupled high performance liquid chromatography (HPLC) to specific radioimmunoassays. Seven follicles were immature (diameter [removed]22 mm) and six were persistent follicles, collected during the luteal phase [15-31 mm, luteinized unruptured follicles (LUF)]. Follicular fluids were extracted by mean of Sep-pak cartridges and then purified by HPLC with a reverse-phase C-18 column eluted in a linear gradient with acetonitrile/0.01 M hydrochloric acid (from 18:82 to 40:60). Fractions were tested with specific antisera for ACTH (1-39), α-MSH, β-lipotropin (β-LPH), β-endorphin (β-EP) and γ-endorphin (γ-EP) immunoreactivities. No presence of β-LPH, β-EP and ACTH was confirmed, while γ-EP, α-MSH and des-α-MSH were detected for the first time in follicular fluid. In every class of follicles shorter chain peptides predominate over their longer chain precursor. Immature follicles are characterized by the highest amounts of γ-EP, ACTH, α-MSH and des-α-MSH if compared to superovulated and LUF. On the contrary, β-EP amount was highest after superovulation. Apart from this finding, peptide levels in superovulated patients and LUF are similar. These results suggest: (a) the presence of almost all of POMC-derived peptides within the follicle, (b) that the processing of this opioid precursor is a function of the ovarian cycle, and (c) that a selective reduction of β-EP in LUF could be related to the lack of follicular rupture. © 1988.