Peripheral Blood and Ovarian Levels of Sex Steroids in the Cyclic Hamster

Abstract

Changes in progesterone (P), testosterone (T), estrone (E₁) and estradiol-17β (E₂) in peripheral blood, ovary, corpora lutea (CL) and in the nonluteal portion of the ovary (NLO) were studied in the cyclic hamster by RIA. In addition, androstenedione (A) was measured, but only in serum. Serum P levels were the same on Days 1 (day of ovulation) and 2 at 0900 h (5 ng/ml), but declined markedly on Day 3 and on the morning of Day 4 (proestrus). After the LH surge on the afternoon of Day 4, serum and ovarian levels of P increased abruptly until 1900 h to 11-18 ng/ml and declined slowly thereafter. Peak T levels in both serum (209 pg/ml) and the ovary occurred between 1400-1500 h of Day 4, paralleling the rising P levels. However, T levels declined rapidly after 1600 h to undetectable levels by 1900 h, but there was a second peak of T by 2300 h in serum which was matched by the ovary.