Effects of aging on luteinizing hormone release in different physiological states of the female golden hamster.
Effects of aging on estrous cycles and LH release in response to luteinizing hormone releasing hormone (LHRH), castration, and estradiol benzoate were studied in the female golden hamster (Mesocricetus auratus). About 80% to 90% of female golden hamsters still cycled regularly when reaching 19-22 months of age. However, some animals showed age-induced irregularity of the estrous cycle which included an interruption or complete absence of estrous vaginal discharge. Young female hamsters (3-5 months) had significantly (p less than 0.01) higher basal LH concentration than old animals (19-22 months) in the morning of each stage of estrous cycle. LHRH elicited about 20-30 fold increase in serum LH concentrations in both young and old hamsters. No significant difference in LH release was observed between young and old hamsters in response to LHRH. In acyclic hamsters, the peak of LH release in response to LHRH was delayed. LHRH-induced LH release was greater in the morning of proestrus than during diestrus in both young and old hamsters. LH increase was significantly greater in the young than in old hamsters on the 13th and 15th day after castration. However, positive feedback stimulation of LH release by estradiol benzoate was the same in both young and old hamsters. These results indicate that in the female hamster, LH response to acute stimuli such as LHRH and estrogens is the same in the young as in the old animal and that circulating basal LH concentration may decrease or its degradation or clearance may increase during the aging process in female golden hamsters. Irregularity of estrous cycles in aging hamsters may be related to delayed responsiveness of pituitary LH to LHRH stimulation.
D000375:Aging; D000818:Animals; D002369:Castration; D006224:Cricetinae; D004958:Estradiol / Q000494:pharmacology; D004971:Estrus; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood*; D010053:Ovary / Q000502:physiology*; D011247:Pregnancy; D013268:Stimulation, Chemical
D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007986:Luteinizing Hormone