Proestrous levels of LH and FSH subsequent to adrenalectomy the same morning.

Adrenalectomies and sham-adrenalectomies were performed on the day of proestrus between 0900 and 1000 hours. On the afternoon and evening of the same day, these animals, as well as unoperated control animals, were sacrificed at 2-hour intervals from 1400 through 2400 hours and blood was taken from the abdominal aorta. Plasma concentrations of LH and FSH were determined by radioimmunoassay. Adrenalectomized, sham-adrenalectomized, and normal rats all show a peak in LH levels at 1800 hours on proestrus. Peak concentrations of FSH were found at 2200 hours in control and adrenalectomized rats, while in the sham-adrenalectomized animals an advancement of the FSH surge by 2 hours, to 2000 hours, was seen.