Plasma and pituitary concentrations of luteinizing hormone, follicle-stimulating hormone and prolactin in aged, ovariectomized CD-1 and C57BL/6 mice.

Plasma and pituitary concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin (Prl) were determined by radioimmunoassay in young (2-4 months-old) and aged CD-1 (14-18 months-old) and C57BL/6 (16-22 months-old) mice one month after ovariectomy. In young, ovariectomized mice, plasma and pituitary concentrations of LH and FSH were significantly higher, whereas concentrations of Prl were significantly lower than those in control mice (sham-operated). In contrast, plasma concentrations of LH, FSH and Prl were not statistically different in aged, ovariectomized mice and aged, control mice. There were also no differences in pituitary concentrations of the three hormones when comparing the same aged C57BL/6 mice, although the aged, ovariectomized CD-1 mice exhibited higher pituitary levels of each hormone than those of their controls. The pituitary of the aged mouse responds differently to ovariectomy than that of the young mouse because of age-related changes in the ovary and/or hypothalamic-hypophyseal complex.