Correlation of age-associated increases in follicle stimulating hormone secretion with decreases in antral follicles: failure of progesterone-induced acyclicity to prevent these changes.
It is well known that the number of follicles in the mammalian ovary decreases with age. In light of previous data from this laboratory showing age-related alterations in the secretion and production of follicle-stimulating hormone (FSH) in rats by 5-6 months of age, one objective of the present study was to determine if alterations in FSH secretion were accompanied by changes in the number of antral follicles. A second objective of this study was to determine whether or not interruption of cyclic activity by continuous progesterone (P) treatment could decelerate age-associated changes in FSH secretion possibly by retarding the depletion of follicles through ovulation. For this study, one group of 4-day cycling, 7-week-old rats received one empty Silastic implant while another group received 3-40 mm implants containing 30 mm crystalline P. Implants were replaced every 2 weeks until the animals were 5 months old. Progesterone-implanted rats were acyclic during treatment exhibiting predominantly leukocytic vaginal smears. Regular 4-day cycles resumed when P implants were withdrawn (rats approximately 5-6-months-old). A group of 2-3-month-old untreated rats were used for comparison. As expected from our previous results, serum FSH levels at 1600 h on estrus were significantly higher in 5-6-month-old rats receiving empty capsules than in younger rats. Serum FSH concentrations measured in P-treated rats at this time also were significantly higher than levels of this gonadotropin measured in younger rats. Ovaries of older control and P-treated rats contained significantly fewer medium and large antral follicles (greater than 250 microns) than the ovaries of younger rats despite the curtailment of estrous cyclicity and ovulation by continuous P treatment. Interestingly, P treatment prevented the age-associated decrease in thymus weight. Taken together, the present observations suggest that a decrease in the number of growing follicles may be a factor contributing to early age-related alterations in FSH secretion. Furthermore, the prevention (at least temporarily) of age-related thymic involution by P treatment may be indicative of an interrelationship between thymic and reproductive aging.
Crawford
K A
KA
Department of Physiology, University of Texas Health Science Center, San Antonio 78284.
Hirshfield
A N
AN
De Paolo
L V
LV
D000375:Aging / Q000473:pathology / Q000502:physiology*; D000818:Animals; D004971:Estrus / Q000187:drug effects / Q000502:physiology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D006080:Ovarian Follicle / Q000187:drug effects / Q000502:physiology*; D011374:Progesterone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013950:Thymus Gland / Q000187:drug effects / Q000473:pathology
D011374:Progesterone; D005640:Follicle Stimulating Hormone