The neurohypophysial peptide hormone oxytocin is associated with
parturition/milk ejection. The identification of a non-neural source
of oxytocin secreted in significant amounts from the ovarian corpus
luteum of ruminants stimulated interest in this octapeptide hormone.
Oxytocin has an ovarian source, whereas an oxytocin-like peptide is
reportedly present in the testes. Highly purified populations of
guinea pig Leydig cells were incubated with a maximally stimulating
dose of 100 ng/ml LH for 24 hours in the presence of increasing
concentrations of sodium ascorbate. Sample supernatants were
extracted, concentrated under vacuum and reconstituted with acidified
absolute ethanol. Samples were analyzed for oxytocin using high
performance liquid chromatography (HPLC) with electrochemical
detection and known concentrations of an authentic oxytocin standard.
Leydig cells stimulated with 0, 25 and 50 uM ascorbate produced and
secreted 40 +/- 1.2, 77 +/- 14 and 74 +/- 26 pg of an oxytocin-like
peptide, respectively, per 1 x 10(6) cells. It would appear that
guinea pig Leydig cells are capable of producing an oxytocin-like
peptide de novo. Low concentrations of ascorbate stimulate the
production of this peptide in Leydig cells cultured in vitro.
Comparison of the amino acid composition and sequence of this oxytocin-
like peptide with authentic oxytocin are already in progress to
confirm whether Leydig cells possess the biosynthetic machinery for
testicular oxytocin production.
Kukucka, Mark A. and Hara P. Misra. 1992. HPLC identification of an
oxytocin-like peptide produced by isolated guinea pig Leydig cells:
stimulation by sodium ascorbate. In: E.S.E. Hafez (Ed), Molecular
Andrology, Volume IV, Issues 1-2, pp 160-161. M.C. Chang Festschrift,