Basal and stimulated LHRH receptor sites in the pituitary of aging female mice

Abstract

We studied the regulation of pituitary luteinizing hormone-releasing hormone (LHRH) receptors in female mice aged 4–8 months (young), 10–14 months (middle-aged) and 15–18 months (old). In intact animals the mean ± SE pituitary content of LHRH receptor sites ranged from 34.4 ± 6.3 fmoles to 41.5 ± 5.0 fmoles and remained constant throughout aging. Similary, receptor affinity for LHRH was unaltered (range 1.0–4.0 ± 109 M⁻¹) by age. Ovariectomy (ovx) resulted in a 30–50% decrease in pituitary LHRH receptor sites (p < 0.05) and the pattern of LHRH receptor fall after ovx was similar in all three age groups. Administration of estrogens (E₂) at either a low (0.2 mg) or a high (2.0 mg) concentration to ovx mice prevented this fall in LHRH receptor sites and, in all three age groups, increased pituitary values to levels comparable to those measured in intact animals. We conclude that there are no significant differences in the basal and stimulated number or affinity of pituitary LHRH receptors between young, middle-aged and aged female mice.