Alterations in LH and FSH Content and Weight of the Anterior Pituitary Gland of Immature Female Rats Treated with PMS

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Abstract
The pituitary content of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) was determined by quantitative bioassay in glands removed during the afternoon of the day preceding PMS [pregnant mare''s serum]-induced ovulation in 27-day-old rats. It was found that no change in pituitary LH occurred between the hours of 2 and 7 pm, but that there was a 32% decrease in pituitary FSH. A significant decrease in pituitary LH was found when a comparison was made between the glandular content at 2 pm on the second and third days after PMS. An examination of pituitary weight in the PMS-treated rats showed a statistically significant hypertrophy during the afternoon of the day preceding ovulation. It was considered that this hypertrophy was due to estrogen stimulation and that ovarian estrogen is probably of primary importance in the positive feedback system which stimulates ovulating hormone (OH) release.