[Autoradiographic study on the distribution of gonadotropin-releasing hormone receptor in the rat ovary].

: Autoradiographic studies were undertaken to clarify the distribution and regulatory mechanisms of GnRH receptors in the ovary of the immature rat during sexual maturation. Iodinated GnRH analog (GnRHa) was injected intravenously and the uptake and distribution of the GnRHa in the ovary were examined. The uptake rate for GnRHa in the ovary increased gradually from 7 days to 21 days of age and declined by 49 days of age. The uptake of GnRHa increased in the ovary of the hypophysectomized rat (28 days old) treated with GnRH and decreased in those treated with PMSG. In the autoradiographic study, silver grains were detected in the ovary, that is the theca cells and the interstitial tissue as well as the granulosa cells. GnRHa bound predominantly to the interstitial tissues before 21 days of age, but GnRHa bound to the granulosa cells more than the theca cells and the interstitial tissue after 28 days of age, corresponding with the prepubertal decrease in GnRHa uptake in the ovary. These results suggest that the distribution of GnRH receptor in the ovary changes with follicular development during sexual maturation.