Serum luteinizing hormone, follicle-stimulating hormone, prolactin and progesterone concentrations and follicular development in the pseudopregnant rat after unilateral ovariectomy.

Serum LH, FSH, prolactin and progesterone concentrations and follicular size were measured in rats during pseudopregnancy after unilateral ovariectomy (ULO) on day 1. This operation did not affect the duration of pseudopregnancy. Following pseudopregnancy compensatory ovulation occurred. After ULO progesterone concentrations remained low as compared with control values but the progesterone secretion per ovary was increased slightly. After ULO, LH concentrations were significantly increased on days 3 and 4 of pseudopregnancy. FSH concentrations were increased 5 h after the operation and again on day 4-7 of pseudopregnancy when compared with sham-operated control animals. During pseudopregnancy prolactin secretion increased each night. Increased prolactin levels were observed 18 and 36 h after ULO. The number of medium-sized follicles had increased 24 h after ULO. From the present study it is concluded that progesterone secretion by the corpora lutea can be increased to a limited degree by the increased release of gonadotrophins. Furthermore, it is concluded that a rapid increase in FSH concentrations after ULO is responsible for the initiation of the compensatory follicular growth.