Plasma and pituitary concentrations of LH, FSH and prolactin in aging Mongolian gerbils

Samples of plasma and pituitary homogenates collected from female Mongolian gerbils (3-4, 11-13 and 20-25 month-old) at various stages of the estrous cycle were analyzed by radioimmunoassay for luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (Prl). Plasma and pituitary LH concentrations were similar in all three age groups. Plasma FSH concentrations tended to increase with age while plasma Prl concentrations remained unchanged. Pituitary concentrations of FSH and Prl were variable between the age groups depending upon the stage of the estrous cycle. The inability of older gerbils to produce young appears to result primarily from age-related changes occurring in the uterus rather than from alterations in the hypothalamic-hypophyseal complex.