Ovarian Follicular Development during the Rat Estrous Cycle: Gonadotropin Receptors and Follicular Responsiveness1

The LH and FSH receptor content in thecal and granulosa cells of large antral follicles was measured by in vitro binding assays and in vivo autoradiography during the rat estrous cycle. Specific binding of [125I]-hCG to granulosa cells increased from <1000 cpm/μg DNA on estrus, metestrus and diestrus to 6000 CPM/μg DNA on proestrus. Specific binding of [125I]-hFSH to granulosa cells was consistently between 2000 and 3000 cpm/μg DNA throughout the cycle. Specific hCG binding to thecal cells also increased between diestrus and proestrus, while specific hFSH binding to thecal cells was essentially nondetectable.