Serum Estradiol and Progesterone Concentrations in Ovariectomized Estrogen– and Progesterone–Primed and PMS–hCG-Treated Rats 1

Summary Estradiol (E2) and progesterone (P) were measured by radioimmunoassay in peripheral blood serum on the second day of diestrus (D–2) and estrus (E) in normal cycling rats, in ovariectomized (OVX) animals, and in PMS–hCG– and OVX–E2–P–treated rats. PMS–hCG and OVX–E2–P animals had significantly higher estradiol and progesterone levels than cycling rats on D–2 or E. Progesterone was significantly higher in the PMS–hCG group while estradiol was higher in OVX–E2–P–treated rats. These results may provide an explanation of previous findings relative to LH dynamics in OVX–E2–P– and PMS–hCG–treated animals. We thank Mrs. Ruth Penardi, Miss Katherine Bangs, and Mrs. Frances Smith for technical and secretarial help and Mr. Bobby McAlister for drawing the figure.