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Identification of cyclo(His-Pro)-like immunoreactivity in human follicular fluid: correlation with steroid and
G C Wolf1, C R Sanborn, D J Thompson
1Department of Obstetrics and Gynecology, University of South Carolina School of Medicine, Columbia 29203, USA.
Objective:
The purpose of this study was to evaluate human follicular fluid (FF) for the presence of cyclo(His-Pro)-like immunoreactivity (CHP-LI). After verifying its presence, we quantitated the levels and investigated correlations with other follicular parameters, including hormone levels.
Methods:
Follicular fluid was collected from female volunteers undergoing controlled ovarian hyperstimulation. Fluid was collected by follicular puncture, either transvaginally (in vitro fertilization) or laparoscopically (gamete intrafallopian transfer) at the time of oocyte retrieval (N = 137). Follicular size was determined ultrasonographically. Assays for steroid and peptide hormones were determined with commercially available radioimmunoassay kits. CHP-LI was measured using a previously reported assay; parallel dilution curves and column chromatography aided in immunoidentity.
Results:
The mean FF CHP-LI concentration (13.10 +/- 1.83 nmol/L, N = 137) was greater than the corresponding serum values (9.42 +/- 2.45 nmol/L; N = 21) (P < .05). Large follicles (20 mm or greater; 14.45 +/- 1.74 nmol/L) contained significantly more CHP-LI than either medium follicles (16-19 mm; 11.51 +/- 1.88 nmol/L) or small follicles (15 mm or smaller; 10.83 +/- 2.12 nmol/L) (P < .05). Positive correlations were found between FF CHP-LI values and corresponding FF progesterone and prolactin concentrations (r = 0.67 and 0.62, respectively; P < .05).
Conclusion:
Mean CHP-LI levels in the FF are greater than those in the corresponding serum. We suggest that the neuropeptide may be originating from either peptidase cleavage of precursor peptides or from granulosa cell production.