Characteristics of Luteal Function in the Superovulated, Pseudopregnant Hamster

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Abstract
Serum concentrations of progesterone, luteinizing hormone (LH), and prolaction (PRL), and luteal binding of 125I-human chorionic gonadotropin (hCG) and 125I-PRL were measured in superovulated hamsters rendered pseudopregnant (PSP) by mating with vasectomized males on Day 0. Animals were killed at 8 h intervals (4-6 per interval) beginning at 1600 h on Day 1 through 0800 h of Day 8, and ovaries and trunk blood collected. Mean serum progesterone was maximal at 0800 h on Day 3 of PSP and, for the most part, remained elevated through PSP until the decline associated with luteolysis occurred between 2400 h of Day 7 and 0800 h of Day 8. Progesterone was positively correlated with the number of corpora lutea (CL) and CL weight (P125I-hCG to CL tissue suggesting that PRL may induce LH receptor. Binding of 125I-hCG to luteal tissue was initially low through Day 3, but became elevated by 1600 h of Day 4 and remained thus until luteolysis ensued between 2400 h of Day 7 and 0800 h of Day 8. The binding of 125I-PRL to luteal membranes was initially high, and fell on Days 2 and 3. Subsequent levels remained low throughout PSP with no apparent change during luteolysis. 125I-PRL binding was not correlated with any other parameter studied, and did not decline with luteolysis.