AJP - Endocrinology and Metabolism, Vol 252, Issue 4 E500-E504, Copyright © 1987 by American Physiological Society
Role of luteinizing hormone in luteotropic complex of pregnant hamster
H. Tamura and G. S. Greenwald
Hamsters were hypophysectomized on day 4 of pregnancy (day 1 = sperm in
vaginal smear) and injected subcutaneously on days 4-7 with various
combinations of 200 micrograms prolactin (Prl), 10 micrograms
follicle-stimulating hormone (FSH), and 20 micrograms luteinizing hormone
(LH) in polyvinylpyrrolidone (PVP) to decrease its rate of absorption or in
saline. End points for luteal function on day 8 were maintenance of
pregnancy, serum progesterone (P4), luteal weight, and luteal binding for
human chorionic gonadotropin, FSH, and Prl. After hypophysectomy, a drastic
decline occurred in all parameters including an 89% decrease in luteal
weight. Injection of Prl did not maintain pregnancy nor serum P4 but
partially maintained luteal weight and human chorionic gonadotropin binding
sites per corpus luteum. The minimal luteotropic complex of Prl and FSH was
effective in maintaining pregnancy and significantly increased serum P4 and
Prl and FSH receptors but not to control levels; Prl and LH (PVP) was also
effective to the same extent. Antral follicles were lacking after either
treatment. The effects of FSH cannot be attributed to LH contamination. All
variables were restored to control levels by Prl plus FSH plus LH (PVP) and
antral follicles were present; Prl plus FSH plus LH (saline), however,
induced luteolysis and reduced most values to the levels found in
untreated, hypophysectomized animals. Thus, the luteotropic activity of LH
was only demonstrable when it was injected in a long-acting form; when
delivered as a bolus, LH (saline) was luteolytic.
