The effects of methyl tert-butyl ether (MTBE) on the male rat reproductive system.

Methyl tert-butyl ether (MTBE) is an oxygenated compound, which has been widely used in Asia, Europe and North America. Although numerous in vitro and in vivo studies have demonstrated the carcinogenicity and the toxicity of MTBE, there is still a lack of data on reproductive system exposure of MTBE in male rodent animals. We studied subacute exposure of MTBE on the reproductive systems of male Sprague-Dawley rats. MTBE was administered to rats at dose levels of 0, 400, 800 and 1600 mg/kg/day. After 2 or 4 weeks of treatments, the rats were euthanized, and their serum, epididymis and testes were collected. Significant adverse effects in their reproductive system were observed including: a significant increase in the percentage of abnormal sperm; an irregular and disordered arrangement of the seminiferous epithelium indicated by a histopathological examination; changed serum levels of testosterone (T), luteinizing hormone (LH) and follicle stimulating hormone (FSH); and decreased levels of mRNA and of androgen binding protein (ABP). In the oxidative stress study, results indicated an increased maleic dialdehyde (MDA) content, implying a raised peroxide level, and that the total antioxidant ability in serum was significantly increased. This finding was especially strong at 1600 mg/kg/day MTBE. In the 2-week treatment, at 1600 mg/kg/day, the mRNA level of 8-oxoguanine DNA glycosidase (OGG1) was significantly decreased, and the mRNA level of the extra-cellular form of superoxide dismutase (SOD(EX)) was significantly increased. Our experiments suggest that relatively high doses of MTBE can exert reproductive system toxicity of male rats and disturb the secretions of T, LH and FSH, possibly due to oxidative stress induced by MTBE.

Effects of Astragalus polysaccharides (APS) on the expression of immune response genes in head kidney, gill and spleen of the common carp, Cyprinus carpio L.

For fish immune defences, cytokines and anti-microbial peptides (lysozyme) in circulating system play important roles. In the present study, the effects of Astragalus polysaccharides (APS) injection on gene expression of interleukin 1beta (IL-1beta), tumor necrosis factoralpha (TNF-alpha) and lysozyme-C in the head kidney, gill and spleen of common carp were determined using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). After injection of APS, IL-1beta mRNA level increased in a dose-dependent manner in the head kidney, while no significant changes were found in the gill and spleen. High dose of APS up regulated TNF-alpha transcription in the gill and spleen, while TNF-alpha mRNA level decreased significantly in the head kidney of low dose of APS. Lysozyme-C mRNA levels were up regulated in the gill of low dose of APS and spleen of middle dose of APS. No effect of the APS on lysozyme-C expression was observed in head kidney. These results constitute a first step toward the understanding of APS effect on cytokines and immune-related gene expression in different organs of common carp.