de novo oxytocin production in Leydig cells
Posted in the Cell Biology Forum
Since: Sep 08
#1 Sep 15, 2008
This is the earliest description of de novo production of authentic
oxytocin in Leydig cells that I can find in the scientific literature:
Mechanisms by which hypoxia augments Leydig cell viability and differentiated cell function in vitro (PhD Dissertation, 1993)
by Mark A. Kukucka, MS, DVM, PhD
Department of Biomedical Sciences
Virginia-Maryland Regional College of Veterinary Medicine
Virginia Polytechnic Institute & State University
Blacksburg, Virginia 24061
The 1980s heralded the discovery and identification of extra-pituitary sources of the neurohypophysial hormone oxytocin in non-neural tissues of several animal species. The presence, location and biosynthesis of significant amounts of oxytocin in the ovarian corpus luteum was followed by the immunocytochemical demonstration of an oxytocin-like peptide in the testicular interstitial cells. Leydig cells, which comprise up to 80% of the testicular intertubular cell population, are known to synthesize testosterone in situ. Indirect evidence indicated that an oxytocin-like peptide was also present in Leydig cells. The question arose whether this peptide was synthesized de novo by Leydig cells or was taken up and stored by the cells following biosynthesis at some other intra- and/or extra-gonadal source(s). Since luteinizing hormone (LH) and ascorbate are known to augment the production of oxytocin in ovarian granulose cells, varying concentrations of these two stimulants were used to monitor the biosynthesis of oxytocin from isolated Leydig cells in culture....
....Using a polyclonal antibody (Ab)-based immunoaffinity column, oxytocin biosynthesis was monitored in Leydig cells incubated with a mildly stimulating dose (0.1 ng/ml) of ovine LH for 24, 48 and 72 hours in the presence of increasing concentrations of sodium ascorbate (1- 500 mM) under culture conditions of hypoxia and normoxia. Following solid phase extraction and immunoaffinity purification, sample supernatants were analyzed for both testosterone and oxytocin content as measured by radioimmunoassay (RIA) and high performance liquid chromatography-electrochemical detection (HPLC-ECD) respectively. Hypoxic culture conditions and low (1-10 mM) concentrations of sodium ascorbate augmented the production of oxytocin from Leydig cells in culture. Higher (50-500 mM) levels of ascorbate and normoxic culture conditions suppressed both testosterone and oxytocin production in isolated Leydig cells. Because oxytocin synthesis was found to be cycloheximide-sensitive, we conclude that Leydig cells possess the biosynthetic machinery necessary to manufacture oxytocin. The isolated oxytocin peptide was purified by HPLC with fraction collection followed by polyclonal-Ab immunoaffinity column chromatography. Comparison of the amino acid sequence of the isolated octapeptide with authentic oxytocin provides unequivocal evidence that Leydig cells synthesize oxytocin de novo. Considering the widespread use of vitamin C as a dietary supplement, the research reported yields valuable mechanistic information on the reproductive biologic role of vitamin C in gonadal steroid and peptide hormone metabolism.
Other publications by Dr. Mark A. Kukucka
#2 Nov 5, 2008
Dr. Mark A. Kukucka theorized in his PhD dissertation that "the redox potential of oxytocin-oxytoceine may drive ascorbate-dehydro-ascorbate or vice versa as part of the non-enzymatic antioxidant defense system."
With that said:
Could the redox potential of oxytoceine drive the formation of reduced ascorbate and oxytocin.... is this chemistry right?
Does anyone know the redox potentials for oxytoceine oxytocin?
Does anyone know the redox potentials for ascorbate dehydroascorbate?
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