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Assessing the effects of low boron diets on embryonic and fetal development in rodents using in vitro and in vivo model systems
- Lanoue, Louise, Taubeneck, Marie W., Muniz, Jesus, Hanna, Lynn A., Strong, Philip L., Murray, F. Jay, Nielsen, Forrest H., Hunt, Curtiss D., Keen, Carl L.
- Biological trace element research 1998 v.66 no.1-3 pp. 271-298
- blastocyst, blood serum, boric acid, boron, breeding, diet, embryogenesis, fetal development, in vitro culture, in vivo studies, liver, mice, pregnancy, rats, toxicity
- To date, boron (B) essentiality has not been conclusively shown in mammals. This article summarizes the results of a series of in vitro and in vivo experiments designed to investigate the role of B in mammalian reproduction. In the first study, rat dams were fed either a low (0.04 μg B/g) or an adequate (2.00 μg B/g) B diet for 6 wk before breeding and through pregnancy; reproductive outcome was monitored on gestation day 20. Although low dietary B significantly lowered maternal blood, liver, and bone B concentrations, it had no marked effects on fetal growth or development. The goal of the second study was to assess the effects of B on the in vitro development of rat postimplantation embryos. Day 10 embryos collected from dams fed either the low or adequate B diets for at least 12 wk were cultured in serum collected from male rats exposed to one of the two dietary B treatments. Dams fed the low B diet had a significantly reduced number of implantation sites compared to dams fed the B-adequate diet. However, embryonic growth in vitro was not affected by B treatment. The aim of study 3 was to define the limits of boric acid (BA) toxicity on mouse preimplantation development in vitro. Two-cell mouse embryos were cultured in media containing graded levels of BA (from 6 to 10,000 μM). Impaired embryonic differentiation and proliferation were observed only when embryos were exposed to high levels of BA (>2000 μM), reflecting a very low level of toxicity of BA on early mouse embryonic development. Study 4 tested the effects of low (0.04 μg B/g) and adequate (2.00 μg B/g) dietary B on the in vitro development of mouse preimplantation embryos. Two-cell embryos obtained from the dams were cultured in vitro for 72 h. Maternal exposure to the low B diet for 10, 12, and 16 wk was associated with a reduction in blastocyst formation, a reduction in blastocyst cell number, and an increased number of degenerates. Collectively, these studies support the concept that B deficiency impairs early embryonic development in rodents.