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Simvastatin and Dipentyl Phthalate Lower Ex vivo Testicular Testosterone Production and Exhibit Additive Effects on Testicular Testosterone and Gene Expression Via Distinct Mechanistic Pathways in the Fetal Rat
Beverly, B., C. Lambright, J. Furr, H. Sampson, V. Wilson, B. McIntyre, P. Foster, G. Travlos, AND E. Gray. Simvastatin and Dipentyl Phthalate Lower Ex vivo Testicular Testosterone Production and Exhibit Additive Effects on Testicular Testosterone and Gene Expression Via Distinct Mechanistic Pathways in the Fetal Rat. TOXICOLOGICAL SCIENCES. Society of Toxicology, RESTON, VA, 141(2):524-37, (2014).
Pharmaceuticals in the environment may disrupt reproductive development in utero by altering fetal hormone production. When exposures are combined with a toxic substance that affects the same hormone the mixture produces additive effects greater than the effect of either chemical. Hence, we need to be concerned about the effects of mixtures of chemicals that disrupt development when the fetus is exposed to such mixtures in utero
Sex differentiation of the male reproductive tract in mammals is driven, in part, by fetal androgen production. In utero, some phthalate esters (PEs) alter fetal Leydig cell differentiation, reducing the expression of several genes associated with steroid synthesis/transport, and consequently, lowering fetal androgen and lnsl3 hormone levels. Simvastatin (SMV) is a cholesterol-lowering drug that directly inhibits HMG-CoA reductase. SMV may also disrupt steroid biosynthesis, but through a different mode of action (MOA) than the PEs. As cholesterol is a precursor of steroid hormone biosynthesis, we hypothesized that in utero exposure to SMV during the critical period of sex differentiation would lower fetal testicular testosterone (T) production without affecting genes involved in cholesterol and androgen synthesis and transport. Secondly, we hypothesized that a mixture of SMV and a PE, which may have different MOAs, would reduce testosterone levels in an additive manner. Pregnant Sprague Dawley rats were dosed orally with SMV, dipentyl phthalate (DPeP), or SMV plus DPeP from gestational days 14-18, and fetuses were evaluated on GD18. On GD18, SMV lowered fetal T production and serum triglycerides, low density lipoprotein, high density lipoprotein, and total cholesterol levels, and downregulated two genes in the fetal testis that were different from those altered by PEs. When SMV and DPeP were administered as a mixture, fetal T production was significantly reduced in an additive manner, thus demonstrating that a mixture of chemicals can induce additive effects on fetal T production even though they display different MOAs.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LABORATORY
TOXICOLOGY ASSESSMENT DIVISION
REPRODUCTIVE TOXICOLOGY BRANCH