Pituitary Follicle-Stimulating Hormone and Luteinizing Hormone Concentrations in Pregnant and Lactating Pigs

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Abstract
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH, ICSH) concentrations were determined in anterior pituitary glands of pigs by the human chorionic gonadotrophin (HCG) augmentation and the ovarian ascorbic acid depletion methods, respectively. Glands were obtained on days 13, 18, 40, 80, 110 of pregnancy and day 14 of lactation. The dry weights of these glands were relatively uniform at days 13, 18 and 40 of pregnancy, but an increase was observed at day 80, which continued until day 14 of lactation. Except for a singificantly low value encountered on day 80 of pregnancy, FSH concentrations were similar throughout pregnancy and lactation. LH concentration increased from day 13 to a maximum at day 18, and then decreased during the remainder of pregnancy. At day 14 of lactation, LH concentration was less than that observed at day 110 of pregnancy. No relationship was found between the rise and fall in FSH and LH, and the number or weight of corpora lutea, or the number of living embryos or fetuses. A trace of LH activity was detected in fetal pituitaries at day 80 of gestation, whereas, by day 110, the concentration had increased to 2.2 [mu]g/mg of dry tissue.