Is the First or Second Periovulatory Surge of FSH Responsible for Follicular Recruitment in the Hamster?

Gilbert S. Greenwald, Harold I. Siegel

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Proestrous hamsters were injected at 1300 hr with phenobarbital to block ovulation. The animals were bled via cardiac puncture every 6 hr beginning at 1600 hr of proestrus until 1000 hr of estrus. The ovaries were then removed and a quantitative evaluation of follicular development carried out. In saline-injected proestrous hamsters, there was a peak of serum FSH and LH at 1600 hr followed by a second prolonged peak of FSH at 0400 and 1000 hr of estrus accompanied by low tonic levels of LH. This hormone profile was associated at 1000 hr of estrus with an average of 9.3 large preantral follicles (stage IV follicles) per ovary. In contrast, the phenobarbital-treated hamsters showed no increases in either gonadotropin at any time and the ovaries contained large antral follicles and an average of only 1.7 stage IV follicles per ovary (three of four animals). Injection of 1 mg progesterone concurrent with phenobarbital restored the first surge of LH but not FSH and partially restored the second peak of serum FSH; the ovaries contained newly formed corpora lutea and 10.5 stage IV follicles per ovary. Injection of 1 μg estradiol along with phenobarbital did not restore the first peak of LH or FSH and partially restored the second FSH surge; the ovaries contained large Graafian follicles but also an average of 10.8 stage IV follicles. Concurrent injection of progesterone and estradiol at the same time as phenobarbital restored the second FSH peak to the magnitude of control values and again the ovaries contained 10.8 stage IV follicles. By using the same animals for periovulatory measurements of gonadotropins and for ovarian histology, these experiments clearly demonstrate that the second prolonged release of FSH is responsible for the recruitment at estrus of the large preantral (stage IV) follicles which represent the pool from which the follicles ovulating 4 days later are selected.

Original languageEnglish (US)
Pages (from-to)225-230
Number of pages6
JournalProceedings of the Society for Experimental Biology and Medicine
Issue number2
StatePublished - Jun 1982

All Science Journal Classification (ASJC) codes

  • General Biochemistry, Genetics and Molecular Biology


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