Oxytocin determination in steroid producing tissues and in vitro production in ovarian follicles

Immunoreactive oxytocin was measured in ovaries (corpus luteum and follicular fluid) and adrenals of cows, and in testes, seminal vesicles, prostate gland and adrenals of bulls. Secretion of oxytocin was further measured after culture of whole follicles, granulosa cells and theca tissue. Concentrations of oxytocin increased in corpora lutea of cycling cattle until mid-luteal phase (447 +/- 93 ng/g wet weight) and decreased afterwards. Low concentrations were found in corpora lutea of pregnant animals (6 +/- 3 ng/g wet weight). Follicular fluid contains some oxytocin (on average 42-108 pg/ml) but concentrations were significantly higher in the fluid of ovarian cysts (190 pg/ml). After culture of follicles the amount of oxytocin released into the medium increased indicating de novo synthesis. The granulosa cells were the main source of follicular oxytocin. Production increased during luteinization indicating that luteinization is an important step for the production of oxytocin in ovaries. Tissues of testes (65 +/- 10 pg/g wet weight) and adrenals from cows (122 +/- 39 pg/g wet weight) and bulls (111 +/- 2 pg/g wet weight) contained oxytocin but at much lower concentrations compared to corpus luteum tissue. About 10 times higher concentrations of oxytocin were measured in the adrenal medulla (717 +/- 96 pg/g wet weight) compared to the cortex (72 +/- 11 pg/g wet weight). Seminal vesicles and prostate gland contained no measurable amounts of oxytocin (less than 5 pg/g wet weight).