PEPTIDES RELATED TO THYROTROPIN-RELEASING-HORMONE (TRH) IN HUMAN PROSTATE AND SEMEN

The TRH-related peptide, pGlu-Glu-ProNH(2), which was first identified in rabbit prostate has recently been named fertilization-promoting pe ptide (FPP) because of its ability to enhance the in vitro fertilizing potential of mouse epididymal spermatozoa. This study set out to exam ine the nature of the TRH-related peptides in human prostate and semen but, first, the optimal conditions for collection of semen samples we re investigated. FPP was degraded slowly (t(1/2) = 163 min, S.E. +/- 5 1.3, n = 6) in seminal plasma which has allowed us to measure accurate ly the concentrations of FPP, after extraction of the peptide in acidi fied acetone precisely 5 min after ejaculation. In this way, high leve ls of FPP (mean: 49.5 nmol/l) were detected in normal human semen, fro m young men, although other TRH-related peptides did not appear to be present. We have also examined the TRH-related peptides present in pro state samples from clinical patients both with and without evidence of benign prostatic hyperplasia (BPH), by ion-exchange chromatography fo llowed by radioimmunoassay. Substantial concentrations of FPP were obs erved in normal (4.10 pmol/g tissue, S.E. +/- 1.46) and BPH prostate ( 6.27 pmol/g tissue, S.E. +/- 1.65). In addition, a second, neutral TRH -immunoreactive peptide was always detected in BPH tissue (7.40 pmol/g tissue, S.E. +/- 1.98) with only low levels generally present in norm al prostate. The possibility that the presence of high levels of the n eutral peptide in prostate may be used as an indicator of the onset of BPH deserves further scrutiny.