Formation of new corpora lutea in mature hypophysectomized rats.

Abstract

New corpora lutea of oviolation were produced in mature hypophysectomized rats by a 4-day regimen of standard FSH and LH preparations. A wide range of gonadotrophin dosages caused luteinization of unruptured fol- licles, which resulted in the formation of corpora lutea atretica. However, oviolation and the forma- tion of 4 or more corpora lutea per rat could be induced consistently only with certain optimum dosages. The subsequent development and func- tion of the induced corpora lutea were also stud- ied. In the absence of further treatment, the in- duced luteal tissue in both types of luteal bodies developed into morphologically persistent but nonfunctional structures similar to those observed in untreated hypophysectomized rats. Prolactin administration, begun on the day after the in- duced ovulation, resulted in functional corpora lutea capable of supporting trauma-induced uterine deciduomata. (Endocrinology 78: 1259, 1966) T HE RELATIVE ease with which ovulation and corpus luteum formation may be in- duced by pituitary gonadotrophins in intact rats contrasts markedly with the results in hypophysectomized animals. This difference, noted in the first experiments with hypophysec- tomized rats (1), was confirmed and extended in later studies using crude preparations of pituitary gonadotrophins (2, 3). These later experiments demonstrated that both dosage and source of extract were critical factors in the induction of ovulation. On the other hand, luteinization of unruptured follicles, sometimes resulting in almost solid luteal bodies (corpora lutea atretica) containing trapped ova, was a consistent observation. Other experiments (4) with purified pituitary preparations revealed that normal ovulation and corpus luteum formation in hypophysecto- mized rats required 4 days of FSH treatment followed by at least 4 or 5 days of combined FSH and LH treatment. The investigators did not note any of the corpora lutea atretica ob- served previously with crude extracts. Carter et al. (5) also obtained normal ovulation and corpus luteum formation with purified prepara- tions. These authors used a treatment regimen approaching the physiological: 4 days of fol- licular development with an ovulatory stimulus on the fourth day. Furthermore, it was ob-