Genistein, a component of soy, was administered to prepubertal female Sprague-Dawley CD rats and investigated for chemoprevention against mammary cancer. Genistein, at 500 microgram/g body wt or an equivalent volume of the vehicle, dimethylsulfoxide (DMSO), was injected (s.c.) on days 16, 18 and 20 post-partum. At day 50 post-partum all animals were exposed to 80 microgram dimethylbenz[a]anthracene (DMBA) per g body wt. Animals treated prepubertally with genistein as compared to DMSO had reduced incidence and significantly fewer adenocarcinomas per animal. Mammary whole mount analysis showed that prepubertal genistein treatment resulted in mammary glands of 50-day-old rats developing fewer terminal end buds and more lobules II. Cell proliferation studies with bromodeoxyuridine (BrdU) showed that terminal end buds from mammary glands of 50-day-old females treated prepubertally with genistein had significantly fewer cells in S-phase of the cell cycle. Serum genistein concentrations in 21- and 50-day-old females following prepubertal genistein treatment were 4.2 +/- 0.6 micromol and 102 +/- 30 nM, respectively. Animals treated prepubertally with genistein as compared to vehicle spent more time in the estrus phase of the estrus cycle, although all animals did cycle. In 50-day-old females, circulating estradiol-17 beta and progesterone concentrations were not significantly altered by the prepubertal genistein treatment. Oocyte/follicle counts and numbers of atretic follicles and corpora lutea were not significantly different between the genistein- and vehicle-treated animals. We conclude that genistein treatment during the prepubertal period can suppress the development of chemically-induced mammary cancer without significant toxicity to the endocrine/reproductive system.

Initial studies of glutamate receptors activated by kainate (KA) found them to be Ca2+ impermeable. Activation of these receptors was thought to produce Ca2+ influx into neurons only indirectly by Na(+)-dependent depolarization. However, Ca2+ entry via AMPA/KA receptors has now been demonstrated in several neuronal types, including cerebellar Purkinje cells. We have investigated whether such Ca2+ influx is sufficient to induce excitotoxicity in cultures of cerebellar neurons enriched for Purkinje cells. Agonists at non-NMDA receptors induced Ca2+ influx in the majority of these cells, as measured by whole-cell voltage clamp and by fura-2 [Ca2+]i microfluorimetry. To assess excitotoxicity, neurons were exposed to agonists for 20 min and cell survival was evaluated by a fluorescence assay 24 hr later. KA (100 microM) reduced neuronal survival relative to controls to 43 +/- 3% when applied in Na(+)-containing solution and to 45 +/- 3% in Na(+)-free solution. This toxicity was blocked completely by CNQX but only slightly by 100 microM Cd2+ and 50 microM D-(-)-2-amino-5-phosphonovaleric acid. Both Purkinje neurons and non-Purkinje cell types present in the cultures were similarly vulnerable to toxic KA exposure, but the population marked by KA-induced Co2+ uptake was selectively diminished by the excitotoxicity. Na(+)-independent excitotoxicity could also be induced by domoate, AMPA, or glutamate. Compared to KA, NMDA was relatively ineffective in inducing cell death. Most of the KA-induced excitotoxicity could be blocked by removal of extracellular Ca2+ during the KA exposure and for a 5 min period thereafter. Furthermore, antagonists of the Ca(2+)-activated enzymes nitric oxide synthase and calpain significantly reduced the KA-induced cell death. These results show that non-NMDA receptor activation can cause excitotoxicity in cerebellar Purkinje neurons by mechanisms not involving Na+ influx, but rather depending on direct Ca2+ permeation and activation of Ca(2+)- dependent enzymatic processes.

Breast cancer is the most common cancer in US females and is the second leading cause of cancer death among women. By contrast, Asian women consuming a traditional diet high in soy products have a relatively low incidence of breast cancer. Asians who emigrate to the United States and adopt a Western diet lose this protection. Soy-based diets are high in phytoestrogens, and one of these components is genistein. Using the dimethylbenz(a)anthracene (DMBA) mammary cancer rodent model, we have investigated the breast cancer protective potential of genistein. Our results demonstrate that neonatal and prepubertal genistein treatments altered the ontogeny of the mammary gland and rendered the adult animals less susceptible to chemically-induced mammary cancer. Neonatal genistein treatment did not significantly alter the rate of formation and persistence of DMBA-DNA adducts in the mammary gland. While high concentrations of genistein during the neonatal period caused adverse effects on ovarian follicular development, prepubertal genistein treatment did not appear to be toxic in either the female reproductive tract or the endocrine system.

Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. .

No abstract