| Sažetak | Selen je esencijalni mikroelement u tragovima, neophodan organizmu u malim količinama, ali toksičan u većim. Možemo ga naći u vodi, tlu i namirnicama životinjskog i biljnog podrijetla jer kao i ostali elementi kruži u ekosustavu. Raspon poželjnih koncentracija selena u ekosustavu je vrlo uzak, a geokemijski se ponaša slično sumporu. Većina biljaka sadrži poprilično nisku koncentraciju Se i dok on nije esencijalan element za biljke, dodavanjem selena u tlo osigurava se da prehrambeni proizvodi sadrže odgovarajuće količine za potrebe ljudi i životinja.
Hrana je primarni izvor Se za ljude i zbog razlika u prehrambenim navikama, njegov unos znatno varira. Identificirano je preko 20 strukturnih selenoproteina i katalitičkih selenoenzima u ljudskom metabolizmu. Oni sudjeluju u antioksidacijskim i protuupalnim procesima, te u proizvodnji hormona štitnjače. Selen je važan sastojak glutation peroksidaze, glavnog staničnog antioksidativnog enzima, koji može pretvoriti slobodne radikale u perokside, dok vitamin E uklanja slobodne radikale i neutralizira njihove potencijalne štetne učinke. Prisutan je u organskoj formi kao Se-aminokiselina, pri čemu su najčešći organski spojevi selenometionin (SeMet), selenocistein (SeCy), dimetilselenid (DMSe), dimetildiselenid (DMDSe), selenometiltranferaza (SMT), Se-metilmetionin (SeMM), glutation peroksidaza (GSH-Px).
U ljudskom organizmu nedostatak selena može dovest do bolesti endokrinog, koštano-mišićnog, kardiovaskularnog, imunološkog, reproduktivnog i živčanog sustava. Dok prekomjerne količine selena u ljudskoj prehrani djeluju toksično i mogu uzrokovati oštećenje jetre i bubrega, zgušnjavanje krvi, nekrozu srca i jetre, kožne lezije, mučninu, povraćanje, gubitak kose i noktiju. Istraživanja provedena u istočnoj Hrvatskoj su pokazala nedostatak selena u tlu, mesu domaćih životinja i žitaricama. Dok su istraživanja provedena u Istri na području Labinštine zbog višestoljetne rudarske tradicije i termoelektrane Plomin pokazala povišene koncentracije selena u ekosustavu.
Prvi dio ovog preglednog rada opisuje i proučava koncentracije selena u tlu, vodi i biljkama, definira i interpretira njegov esencijalni i toksikološki utjecaj na životinje i ljude, dok se drugi dio rada fokusira na analizu i usporedbu dostupne literature o istraživanjima selena provedenim u RH. |
| Sažetak (engleski) | Selenium is an essential trace microelement, that is necessary for organisms in small quantities, but toxic in larger ones. It can be found in water, soil and foods of animal and plant origin because like other elements it circulates throughout the ecosystem. The range of desirable selenium concentrations in the ecosystem is narrow and the microelement behaves geochemically similar to sulfur. Most plants contain a fairly low concentration of Se and while it is not an essential element for plants, adding selenium to the soil ensures that food products contain adequate amounts for human nutritional needs.
Food is the primary source of Se for humans and due to differences in eating habits, its intake varies considerably. Over 20 structural selenoproteins and catalytic selenoenzymes have been identified in the human metabolism. They participate in antioxidant and antiinflammatory processes and also in the production of thyroid hormones. In the human body, selenium deficiency can lead to diseases of the endocrine, musculoskeletal, cardiovascular, reproductive, nervous and immune systems. Selenium is an important ingredient in glutathione peroxidase and it is considered the main cellular antioxidant enzyme, which can convert free radicals into peroxides, while vitamin E removes free radicals and neutralizes their potential harmful effects. It is present in organic form as a Se-amino acid, with the most common organic compounds being selenomethionine (SeMet), selenocysteine (SeCy), dimethyl selenide (DMSe), dimethyldiselenide (DMDSe), selenomethyltransferase (SMT), Se-methylmethionine (SeMM), glutathione peroxidase (GSH-Px).
While excessive amounts of selenium in the human diet are considered toxic and can cause liver and kidney damage, blood clotting, heart and liver necrosis, skin lesions, nausea, vomiting, loss of hair and nails. Research conducted in eastern Croatia has shown a lack of selenium in the soil, meat of domestic animals and cereals. While research conducted in Istria in the Labinštine region has shown that due to centuries of mining tradition and the Plomin thermal power plant there are elevated concentrations of selenium in the ecosystem.
The first part of this review paper describes and studies selenium concentrations in soil, water and plants, defines and interprets its essential and toxicological effects on animals and humans, while the second part focuses on the analysis and comparison of available literature on selenium research conducted in Croatia. |
