title: Exposure to phytoestrogens in the perinatal period affects androgen secretion by testicular Leydig cells in the adult rat.
abstract: The use of soy-based products in the diet of infants has raised concerns regarding the reproductive toxicity of genistein and daidzein, the predominant isoflavones in soybeans with estrogenic activity. Time-bred Long-Evans dams were fed diets containing 0, 5, 50, 500, or 1000 ppm of soy isoflavones from gestational d 12 until weaning at d 21 postpartum. Male rats in all groups were fed soy-free diets from postnatal d 21 until 90 d of age. The mean +/- SD concentration of unconjugated (i.e. biologically active) genistein and daidzein in serum from the group of dams maintained on the diet containing the highest amount of isoflavones (1000 ppm) were 17 +/- 27 and 56 +/- 30 nM, respectively, at d 21 postpartum. The concentrations were considerably greater in male offspring (genistein: 73 +/- 46 nM; daidzein: 106 +/- 53 nM). Although steroidogenesis was decreased in individual Leydig cells, male rats from the highest exposure group (1000 ppm diet) exhibited elevated serum levels of the sex steroid hormones androsterone at 21 d (control: 15 +/- 1.5 vs.28 +/- 3.5 ng/ml; P < 0.05) and testosterone at 90 d of age (control: 7.5 +/- 1 vs.17 +/- 2 ng/ml; P < 0.05). Testosterone secretion by immature Leydig cells, isolated from 35-d-old male rats, decreased on exposure to 0.1 nm genistein in vitro (control: 175 +/- 5 vs. 117 +/- 3 ng/10(6) cells per 24 h; P < 0.05), indicative of direct phytoestrogen action. Thus, phytoestrogens have the ability to regulate Leydig cells, and additional studies to assess potential adverse effects of dietary soy-based products on reproductive tract development in neonates are warranted.
authors.affiliation: Department of Anatomy, Physiology and Pharmacology, 109 Greene Hall, Auburn University, Auburn, Alabama 36849, USA. akingbt@auburn.edu
authors.forename: Benson T
authors.initials: BT
authors.lastname: Akingbemi
authors.forename: Tim D
authors.initials: TD
authors.lastname: Braden
authors.forename: Barbara W
authors.initials: BW
authors.lastname: Kemppainen
authors.forename: Karen D
authors.initials: KD
authors.lastname: Hancock
authors.forename: Jessica D
authors.initials: JD
authors.lastname: Sherrill
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Cook
authors.forename: Xiaoying
authors.initials: X
authors.lastname: He
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Supko
mesh_terms: D000728:Androgens / Q000378:metabolism*; D000818:Animals; D005260:Female; D005865:Gestational Age; D007529:Isoflavones / Q000494:pharmacology*; D007985:Leydig Cells / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D048789:Phytoestrogens / Q000494:pharmacology*; D011247:Pregnancy; D051381:Rats; D020318:Rats, Long-Evans; D013552:Swine; D013737:Testis / Q000187:drug effects / Q000196:embryology*
chemical_list: D000728:Androgens; D007529:Isoflavones; D048789:Phytoestrogens