Patterns of Sex Steroid and Gonadotropin Secretion in Aging Female Rats*

Abstract

Serum estradiol, progesterone, LH, and FSH were determined by RIA in 20- to 30-month-old constant estrous (CE), irregular pseudopregnant (PP), and anestrous (AS) female rats and from 4- to 5-month-old cycling female rats. Disruption of the estrous cycle in aging rats was associated with major changes in secretion of pituitary gonadotropins and ovarian steroids. None of the old rats, in contrast to the young rats, showed cyclic changes in any of the hormones studied. Serum progesterone was much higher in the PP than in the other two old groups, serum estradiol averaged somewhat higher in the CE than in the other two aged groups, and all four hormones were lower in the AS rats than in any other group. Basal serum FSH values were higher in the old CE rats than in either of the other old age groups and were slightly higher than in young rats on the afternoon of proestrus or morning of estrus. Serum FSH values were lower in the old PP and AS rats than in young rats on the afternoon of proestrus or morning of estrus. Serum FSH values were lower in the old PP and AS rats than in young rats on the afternoon of proestrus or morning of estrus. Serum values in the old CE rats were about the same as in young rats on the morning of proestrus or estrus, about the same in old PP rats as in young rats during diestrus, and were undectable in old AS rats. Since the ovaries of old rats are capable of near normal function under appropriate gonadotropic stimulation, it is concluded that the major cause for cessation of regular estrous cycles in old rats lies in altered hypothalamo-pituitary function.

Dysregulation of IGF-I signaling in uterine leiomyoma

“…PE leiomyomas contained more IGF-I message than PP or AT tumors, implying the presence of a stimulus to IGF-I synthesis. Contradictions exist in the literature as to whether E 2 concentrations in PE animals are elevated (Huang et al 1978, Lu et al 1979, but the thickening and keratinization of the vaginal epithelium characteristic of PE animals implies that an estrogenic stimulus also exists during this stage of reproductive senescence. The tyrosine phosphorylation status of IRS-1 in leiomyomas separated by stage of reproductive senescence and age-matched myometrium (three stages combined) was analyzed by immunoprecipitation for IRS-1 followed by Western blotting for tyrosine-phosphorylated proteins.…”

Determinants of uterine aging: lessons from rodent models

“…Eventually the old rats become anestrus. The ovaries and uterus are atrophic, no mature follicles are present, and the uterus resembles that from an ovariectomized or immature rat, which resulted from low circulation level of steroid hormone [51]. Despite that the hormone profile changes account for the uterine abnormality, the senescing endometrium does not respond to ovarian hormones as well as that in young animals [52].…”

Social recognition memory: Influence of age, sex, and ovarian hormonal status

“…During reproductive senescence, aging female rats undergo a loss of cyclicity but (in contrast to humans) continue to maintain constant, moderate levels of ovarian hormones [26,27]. Around 12-14 months, females enter one of two "estropausal" states; typically, they alternate between them for some months before settling in one or the other and then (if they live long enough) become anestrus.…”