CHANGES IN PITUITARY FSH AND LH AND PLASMA LH IN IMMATURE RATS TREATED WITH PREGNANT MARE'S SERUM
ABSTRACT The concentrations of LH and FSH in the pituitary gland and LH in the plasma from immature rats treated with saline, 3 IU, or 12 IU PMS were measured for 4 days. There was no detectable LH in 1.5 ml of plasma at any time in saline-treated rats. In 3 IU PMS rats, an elevation was observed at 3.00 p. m. and 8.00 p. m. on day 24. The plasma LH level of 12 IU PHS rats was much higher than that of 3 IU PMS rats, reaching a maximum at 10.00 a. m. on day 23, then gradually decreasing until the morning of day 25. The pituitary FSH content in 3 IU PMS rats reached a maximum at 10.00 a. m. on day 24, then drastically decreased at 3.00 p. m. and 8.00 p. m. The pituitary FSH content of 12 IU PMS rats showed a gradual decrease without an acute release on the afternoon of day 24. These results indicate that FSH, like LH, is released on the afternoon of day 24 and may be involved in ovulation. The failure of 12 IU PMS rats to ovulate is probably due to (a) interference in the timing of ovulating hormone (OH) release, (b) lack of a surge of LH, or (c) improper ratio of LH to FSH.