GONADOTROPIN-RELEASING-HORMONE RECEPTOR MESSENGER-RIBONUCLEIC-ACID EXPRESSION IN RAT OVARY

Rat GnRH pituitary receptor complementary DNA was used to isolate a tr uncated clone from a rat corpus luteum complementary DNA library that proved to be identical in sequence to the rat anterior pituitary GnRH receptor. The distribution of the GnRH receptor messenger RNA (mRNA) w as then determined in rat ovary using in situ hybridization. GnRH rece ptor expression was investigated in cyclic female rats and in hypophys ectomized immature female rats treated with either recombinant human F SH or human menopausal gonadotropin. The expression of LH receptor mRN A was determined in serial sections as an index of the health and diff erentiation of the follicles. In cyclic animals, GnRH receptor mRNA wa s detected in granulosa cells at varying stages of follicular developm ent and in the corpus luteum. Ovaries from hypophysectomized animals e xpressed GnRH receptor mRNA in the granulosa cells of most follicles. The administration of FSH or human menopausal gonadotropin to hypophys ectomized animals altered the distribution of GnRH receptor mRNA. Duri ng antral development, the signal was most abundant in medium-sized fo llicles not expressing LH receptor mRNA and showing signs of follicula r atresia. However, healthy preovulatory follicles also expressed GnRH receptor mRNA. We conclude that the expression of the GnRH receptor g ene in granulosa cells is 1) individually regulated for each follicle, 2) persists in the corpus luteum, and 3) expressed in atretic follicl es.