Abstract
Summary
A composite profile was made of peripheral progesterone (P) levels at 2-hr intervals over the 4-day estrous cycle of the hamster. Specifically, each of four groups of animals was bled via cardiac puncture (0.08 ml blood/bleeding), without anesthesia, at 2-hr intervals for a 24-hr period starting at 0800 hr on different days of the cycle. P was measured in etheric extracts of serum by RIA. After a fairly steady threefold increase in P from 1000 to 1800 hr on Day 1 (day of ovulation and vaginal discharge), P levels remained relatively stable at 4-6 ng/ml until 2400 hr on Day 2. During the first 6 hr on Day 3, P levels declined to near nondetectable values (<1 ng/ml) and thereafter fluctuated little until the dramatic preovulatory rise began between 1200 and 1400 hr on Day 4 (to 11-13 ng/ml by 1600 hr). After 2400 hr on Day 4, levels of P declined to 4-6 ng/ml by 0600 hr on Day 1. Series of close-interval, episodic fluctuations in P levels were not found.
This research was supported in part by Grant HD-11103 from NICHHD.
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