Plasma Concentration of LH, FSH, Prolactin, Progesterone and Estradiol-17β Throughout the 4-Day Estrous Cycle of the Rat

TLDR

Female rats were sampled every 3 hours over a 4‑day estrous cycle and plasma levels of LH, FSH, prolactin, progesterone, and estradiol‑17β were quantified by radioimmunoassay (progesterone by competitive protein‑binding assay). All five hormones peaked during proestrus; progesterone remained elevated from early metestrus to early diestrus, prolactin spiked briefly at 1500 hr estrus, and estradiol rose late metestrus, peaked at noon proestrus, and fell before the other hormones’ peaks, with LH, prolactin, and progesterone rising preovulatory between noon and midnight proestrus and FSH peaking from noon proestrus to noon estrus. Endocrinology 94:1704 (1974).

Abstract

Groups of female rats were decapitated at 3-hr intervals throughout 4-day estrous cycles and the plasma of each rat was assayed for LH, FSH, prolactin, progesterone and estradiol-17β. Radioimmunoassays were used to measure these hormones, except for progesterone which was determined by the competitive protein binding assay. All five hormones exhibited a peak concentration in plasma on the day of proestrus. In addition, progesterone was elevated from 0900 hr of metestrus to 0900 hr of diestrus, while plasma prolactin showed a brief rise at 1500 hr of estrus. The elevated level of estradiol on the day of proestrus followed a different pattern than the other four hormones. Estradiol concentration began to rise late on metestrus, reached a peak at noon of proestrus, and fell before peak levels of the other hormones were reached. The preovulatory elevation of LH, prolactin and progesterone occurred between noon and midnight of proestrus, while the peak of FSH lasted from noon of proestrus to noon of estrus. (Endocrinology94: 1704, 1974)