Neurotrophin-3 augments steroid secretion by hamster ovarian follicles in vitro

Innervation of the ovary is known to be affected by neurotrophic factors; mRNA for some of these molecules and their low-affinity receptors have been identified in ovarian follicular tissue. We attempted to determine whether neurotrophin (NT-3) exerts a non-neuronal impact on the ovary, affecting follicular estradiol secretion via a possible humoral action. Ovaries were excised from mature Golden Syrian Hamsters (Mesocricetus auratus) and large preovulatory follicles were removed by microdissection. Follicles were incubated for 72 hr in control medium, or medium containing 10 ng, 100 ng, or 1000 ng/ml NT-3. After culture, medium samples were assayed for estradiol content. NT-3 exerted dichotomous effects, depending on concentration: NT-3 augmented mean estradiol output two-fold at 100 ng/ml, while 1000 ng/ml NT-3 decreased estradiol secretion back to control levels. By 48-72 hr in culture, all groups exhibited a significant decline in mean estradiol secretion due presumably to diminished viability, independent of neurotrophin action. These data suggest a humoral role for NT-3 in estradiol secretion of preovulatory follicles in culture.