[Show abstract][Hide abstract] ABSTRACT: IGF-I is a critical regulator of uterine growth, and locally produced uterine IGF-I could mediate the effects of 17beta-E2 on growth and cellular proliferation. We used IGF-I knockout (KO) mice and tissue grafting to determine the roles of local and systemic IGF-I in uterine growth and E2 responsiveness. Uteri from adult KO mice and neonatal and adult wild-type (WT) mice were grown under the renal capsule of female athymic mice for 4 wk. Initial uterine weights of adult KO and neonatal WT mice were 5% or less of those of adult WT uteri. Weights of adult WT uterine grafts did not increase during grafting. Weights of adult KO and neonatal WT uteri exposed to normal systemic levels of IGF-I in athymic hosts increased 20- to 30-fold to equal or exceed those of adult WT grafts. Uterine epithelial height, reduced in KO mice, was restored to WT levels in KO uteri grafted into athymic hosts. The absence of local IGF-I production in KO uteri did not impair E2- induced epithelial proliferation in KO uterine grafts. Neonatal WT uteri grafted into KO hosts showed minimal growth, providing evidence that local uterine IGF-I production is insufficient to support uterine growth in the absence of systemic IGF-I. E2 treatment of KO females produced minimal uterine growth, confirming that lack of IGF-I, rather than E2, caused the uterine hypoplasia. In summary, systemic IGF-I supports normal uterine growth and E2 response in the absence of local IGF-I. Local IGF-I is not a direct mediator of E2 action in uterus, and systemic IGF-I may be more important than previously thought for growth of the uterus and other tissues.
[Show abstract][Hide abstract] ABSTRACT: Use of soy-based infant formulas and soy/isoflavone supplements has aroused concern because of potential estrogenic effects of the soy isoflavones genistein and daidzein. Here we show that s.c. genistein injections in ovariectomized adult mice produced dose-responsive decreases in thymic weight of up to 80%. Genistein's thymic effects occurred through both estrogen receptor (ER) and non-ER-mediated mechanisms, as the genistein effects on thymus were only partially blocked by the ER antagonist ICI 182,780. Genistein decreased thymocyte numbers up to 86% and doubled apoptosis, indicating that the mechanism of the genistein effect on loss of thymocytes is caused in part by increased apoptosis. Genistein injection caused decreases in relative percentages of thymic CD4(+)CD8(-) and double-positive CD4(+)CD8(+) thymocytes, providing evidence that genistein may affect early thymocyte maturation and the maturation of the CD4(+)CD8(-) helper T cell lineage. Decreases in the relative percentages of CD4(+)CD8(-) thymocytes were accompanied by decreases in relative percentages of splenic CD4(+)CD8(-) cells and a systemic lymphocytopenia. In addition, genistein produced suppression of humoral immunity. Genistein injected at 8 mg/kg per day produced serum genistein levels comparable to those reported in soy-fed human infants, and this dose caused significant thymic and immune changes in mice. Critically, dietary genistein at concentrations that produced serum genistein levels substantially less than those in soy-fed infants produced marked thymic atrophy. These results raise the possibility that serum genistein concentrations found in soy-fed infants may be capable of producing thymic and immune abnormalities, as suggested by previous reports of immune impairments in soy-fed human infants.
Preview · Article · Jun 2002 · Proceedings of the National Academy of Sciences