Growth hormone but not prolactin concentrations in the fluid of bovine ovarian cysts are related to the cystic stage of luteinization

Regulation of follicular growth and ovulation as well as steroid production by the ovary depends principally on gonadotropins. However nonsteroid systemic hormones and autocrine and paracrine factors contribute to the regulation of ovarian function. The objectives of the present work were 1) to asses the presence of growth hormone (GH) and prolactin (PRL) in fluid drawn from normal bovine ovarian follicles, cysts or cystic corpora lutea; 2) to relate the stage of luteinization of the cyst with the GH and PRL concentrations in fluids; and 3) to asses the feasibility of providing a defined nonsteroid hormone marker to distinguish between normal and pathological ovarian structures. Cysts were classified according to histological and morphological appearance as follicular or luteal. Concentrations of GH, PRL, estrogens (E(2)), progesterone (P-4) and testosterone (T) were measured in follicular and cystic fluids. On the basis of the E(2) to P-4 ratio, ovarian formation classes were further divided into two subclasses (E(2) dominant and P-4 dominant). The results provide evidence of 1) the presence of immunoreactive GH and PRL in all the follicular and cystic fluids assayed, 2) an increasing concentration of GH correlated to the stage of luteinization of the cyst and a direct correlation between GH and P-4 concentrations, 3) a significant variability of intraovarian fluid PRL concentration not related to the histological class of the cyst nor to the concentrations of steroid hormones examined, and 4) the possibility of distinguishing 6 different ovarian formation classes by merely measuring GH, P-4, E(2) and T concentrations in fluids. These data contribute to a better understanding of the endocrine milieu of bovine ovarian cystic degeneration.