coumestrol and gamma-sitosterol

Phytosterols are natural constituents of the human diet, and as part of an extensive programme of safety evaluation studies investigating their use as a novel food ingredient, the possible oestrogenic effects of phytosterols have been investigated using a combination of in vitro and in vivo assays. Competitive binding with the immature rat uterine oestrogen receptor (ER) has been used to measure the ability of phytosterols to bind to ERs while the transcriptional activation of oestrogen-responsive genes has been examined in an oestrogen-inducible yeast screen. Phytosterols did not display any activity in these in vitro assays. Uterotrophic assays have been conducted to investigate the potential for phytosterols to elicit an oestrogenic response when administered orally to immature female rats (n = 10) at doses of 0, 5, 50 or 500 mg/kg/day for 3 consecutive days. Phytosterols (a well characterized mixture of beta-sitosterol, campesterol and stigmasterol) and phytosterol esters (the previous phytosterol mixture esterified with fatty acids from sunflower oil) did not exhibit oestrogenic activity in the immature female rat using uterine wet weight as the endpoint. Beta-oestradiol (0.4 mg/kg/day) consistently produced a significant increase in uterus weights. Coumestrol (a known phytoestrogen) was also tested as a weak positive control and produced a dose response at doses of 20, 40 and 80 mg/kg/day in the uterotrophic assay. In conclusion, we have shown that phytosterols do not bind to the ER and do not stimulate transcriptional activity of the human ER in a recombinant yeast strain. In addition, there was no indication of oestrogenicity from the uterotrophic assay when the material was administered by oral gavage to immature female rats.

Topics: Administration, Oral; Animals; Binding, Competitive; Cholesterol; Coumestrol; Dose-Response Relationship, Drug; Esters; Estradiol; Estrogens, Non-Steroidal; Female; Organ Size; Phytosterols; Rats; Rats, Wistar; Receptors, Estrogen; Saccharomyces cerevisiae; Sitosterols; Stigmasterol; Uterus

The neonatal hormone environment influences the sexually differentiated patterns of development. Estrogens, derived from intracerebral aromatization, promote male pattern development of the central nervous system. The purpose of this study was to determine the effects of neonatal exposure to environmental estrogens on luteinizing hormone (LH) secretion and development of the sexually dimorphic nucleus of the medial preoptic area (SDN-POA) in castrated adult rats. Neonatal rats of both sexes received injections of either corn oil, 0.1 microgram diethylstilbestrol (DES), 3 micrograms beta-sitosterol (B1), 30 micrograms beta-sitosterol (B2), 0.1 microgram coumestrol (C1), 1 microgram coumestrol (C2), or 10 micrograms coumestrol (C3) on Day 1-10 of life and were castrated on Day 21. Right heart catheters were placed on Day 42, and GnRH (50 ng/kg) was administered. Blood was sampled for LH at 0-, 5-, 10-, 15-, and 30-min intervals. All doses of beta-sitosterol and coumestrol elicited increased basal levels of LH in females. In males, B1, B2, C2, and C3 increased basal levels of LH. The GnRH-induced LH increase was prevented in females treated with diethylstilbestrol and 10 micrograms of coumestrol. Males in all treatment groups exhibited GnRH-induced LH surges. The animals were sacrificed by decapitation on Day 49. Volumes of the SDN-POA of the groups were compared. Treatment with the agents did not result in significantly increased SDN volume in females; nor was there a difference in SDN size among the male groups. These data show that exposure to environmental estrogens early in development alters both postpubertal pituitary response to GnRH and basal LH secretion in females and alters only basal LH secretion in males. No significant enlargement (i.e., masculinization) of the SDN-POA was exhibited.

Topics: Animals; Animals, Newborn; Castration; Coumestrol; Diethylstilbestrol; Female; Gonadotropin-Releasing Hormone; Hypothalamus; Luteinizing Hormone; Male; Pituitary Gland; Rats; Sex Differentiation; Sitosterols