Estrogen-producing ovarian granulosa cells: use of the granulosa cell aromatase bioassay (GAB) to monitor FSH levels in body fluids.

Abstract

FSH is a key inducer of ovarian follicular and testicular tubule developments. During reproductive life, FSH is released in an orchestrated fashion subject to endocrine control. However, the microheterogeneity of the FSH molecule suggests that studies on circulating FSH bioactivity are essential to understanding gonadal development and function. The study of potential paracrine modulators (estrogens, androgens and growth factors) that could enhance FSH action in granulosa cells and therefore have potential physiologic roles in the development of the dominant follicle led to the development of an in vitro bioassay for FSH. The combined action of enhancing hormones and factors resulted in a granulosa cell assay highly sensitive to the aromatase-inducing action of FSH. This assay is hormone-specific and sensitive, and has been applied to the measurement of FSH bioactivity in serum samples through the use of pre-treatment of serum with polyethylene glycol to remove substances inhibitory in the granulosa cell culture. Recent applications of this assay to human and animal serum and urine samples reveal that physiologic levels of FSH can be measured by this assay. Although bioactive FSH levels in serum and urine samples throughout the normal menstrual cycle generally reflect changes in immunoreactive FSH in serum, substantial decreases in B/I ratio of serum FSH were detected in aging men and normal males treated with a GnRH antagonist. Further applications of the Granulosa Cell Aromatase Bioassay (GAB) in different animals species as well as to other physiologic and pathophysiologic states in humans should be rewarding.