Deceleration of age-associated changes in the preovulatory but not secondary follicle-stimulating hormone surge by progesterone.
Recently, it has been reported that mating can delay the age-associated decline in reproductive function of female rats. Since circulating progesterone (P) levels are elevated for a 2- to 3-wk interval during pregnancy, the following study was conducted to determine whether intermittent elevation in P levels can alter the rate of reproductive aging in female rats. Beginning at 2 mo of age, 4-day-cycling, virgin rats were divided into two groups. In one group, 3 Silastic capsules containing crystalline P were inserted s.c. into each rat while rats in another group each received 1 empty capsule. After 2 wk, the capsules were removed for 2 wk. Thereafter, implantation and removal of capsules was repeated 5 additional times. Rats receiving P capsules became acyclic 3-4 days after exposure to P and resumed cyclicity 4-7 days after removal of P-capsules. One month after the last series of capsules was removed (rats approximately 8-mo-old), rats exhibiting consecutive 4-day cycles were inserted with indwelling atrial cannulae and bled at 4-h intervals from 1400 h on proestrus (Pr) to 1000 h on estrus (E). At 1600 h E, rats were killed and trunk blood was collected. For comparison, a group of 3-mo-old (young) rats was bled on Pr and E. In 8-mo-old rats that received empty capsules, 27% exhibited 4-day cycles compared to 66% of the young rats. However, in contrast to rats that received empty capsules, 63.1% of P-treated rats exhibited 4-day cycles. Surges of preovulatory luteinizing hormone (LH) and follicle-stimulating hormone (FSH) surges were attenuated in 8-mo-old rats given empty capsules compared to young rats.(ABSTRACT TRUNCATED AT 250 WORDS)
D000367:Age Factors; D000818:Animals; D003307:Copulation; D004971:Estrus / Q000187:drug effects*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood*; D007986:Luteinizing Hormone / Q000097:blood; D010060:Ovulation / Q000187:drug effects; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D011374:Progesterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone