Autoradiographic Analysis of Gonadotropin Binding to Rat Ovarian Tissue Sections

Abstract

Autoradiographic analysis of serial frozen tissue sections revealed that radioiodinated protein hormones, applied topically, were bound specifically and selectively to target tissues. To study relationships between the functional state of target tissues and protein hormone binding, autoradiographic analysis was performed on ovaries from rats with different known physiologic states. Changes in ovarian and pituitary function were assessed by radioimmunoassay of progesterone, luteinizing hormone (LH), follicle stimulating hormone (FSH), and prolactin in serum. Corpora lutea and interstitial tissue bound labeled rat growth hormone, ovine prolactin, and human chorionic gonadotropin (hCG). The extent of this binding varied with endogenous hormone concentrations and with the functional state of the ovary. At all times, thecal cells bound labeled hCG and granulosa cells of some moderate to large follicles bound labeled FSH. Granulosa cells bound other hormones variably. These results indicate the existence of specific intraovarian tissue-hormone binding, presumably to receptors, and suggest that this receptor activity varies with the functional state of the intraovarian tissues.