Graduate Thesis Or Dissertation
 

Interaction of selenium with cadmium and mercury in semen and reproductive tissues: in vivo and in vitro studies

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  • Studies were conducted to investigate the metabolism of selenium (Se) , and the influences of Se on the metabolism of cadmium (Cd) and inorganic mercury (Hg) in rats, and in ram semen in vitro. Se-deficient (-Se) or Se-adequate (+Se) rats were injected intraperitoneally with either ¹⁰⁹CdCl₂ (5 μCi/rat) or ²⁰³HgN0₃ (10 μCi/rat). Semen ejaculates from yearling Suffolk rams were used for the in vitro studies. Whole-body retention of Cd and Hg in rats was significantly (P < 0.05) increased by Se. However, regardless of the Se status, the predominant route of Cd and Hg excretion was feces. Data on whole tissue Cd retention for both -Se and +Se rats gave the following order of decreasing tissue Cd levels: liver > kidney > testis > epididymis > seminal vesicles > prostate > brain. Hg distribution in tissues followed a similar order except that Hg concentrations were highest in kidney. Se caused a significant redistribution of Cd and Hg among the cytosolic proteins in some tissues (e.g., testis) but not in others like brain and prostate gland. Such diversions were usually from low (10,000 - 30,000) molecular weight (MW) proteins to higher (>70,000) MW ones. Ram sperm incorporated small amounts of Cd and Hg in vitro. A non-thionein metal-binding protein (MW = 10,000) was purified from the spermatozoa, and found to contain low amounts of cysteine and some aromatic amino acids (phenylalanine and tyrosine). Evidence was obtained which suggests that spermatozoa from rats and rams are capable of converting inorganic Se (as selenite) into selenoamino acids both in vivo and in vi tro. Amino acid analyses of sperm hydrolysates showed that selenocystine and selenomethio nine were respectively the major chemical forms of Se in rat and ram spermatozoa. Cd and Hg concentrations ranging from 10⁻⁶ to 10⁻² M were shown to be injurious to ram sperm in vitro as indicated by the depressed motility and reduced oxygen uptake. Equimolar concentrations of Se as selenite, selenocystine or selenomethionine counteracted the toxicity of Cd or Hg at low concentrations (10⁻⁵ to 10⁻⁶ M). Incubation of ram spermatozoa with concentrations of Se ranging from 0.08 to 2.0 ppm markedly improved sperm motility and oxygen consumption.
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Déclaration de droits
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file details AlabiNathanielS1984.pdf 2017-08-16 Public Télécharger