engleski

Metal distribution among gut content, intestinal tissue and cytosol of chub (Leuciscus cephalus L.) from Sava River

Gastrointestinal tissue represents the first target for dietary metal uptake in freshwater fish. Dietary metal distribution is studied in chub (Leuciscus cephalus L.) collected in spring at six locations of Sava River. Copper, Zn, Cd, Mn and Fe partitioning is studied among metal-input fraction (gut content), metal-sensitive fraction (anterior and posterior part of intestine cytosol and tissue, total proteins) and detoxified metal fraction (metallothionein). Metal levels were measured by air-acetylene flame (Zn, Fe) and graphite furnace (Cu, Mn, Cd) Atomic Absorption Spectrometer in cytosol and fractions obtained by microwave digestion (gut content and tissue). Other parameters are analysed after tissue homogenisation, centrifugation at 50000xg (cytosol- total proteins by Lowry procedure) and heat treatment at 85°C (metallothioneins by differential pulse polarography). Metal distribution follows the order: gut content>tissue>cytosol, except for Zn: tissue>cytosol>gut content. In tissue and cytosol metal concentrations decrease as follows: Zn>Fe>Cu=Mn>Cd and in gut content: Fe>Mn>Zn>Cu>Cd. The lowest variations in tissue and cytosol of fish from six stations exist for strongly regulated essential metals, Zn and Cu. Metallothionein levels also remain constant, like metallothionein inducers, Zn and Cu. Iron and Mn reflect the gut content levels, which decrease to downstream locations. The same trend exists for total proteins, which implicates Fe and Mn connection to cytosolic proteins. The highest site-specific metal variations occur in chub gut content. Metal levels in cytosol, the fraction where metal regulation occurs, reflect the levels in intestine tissue. Anterior and posterior comparison indicates higher Fe, Cd and Mn (only tissue) levels in posterior intestine.

chub; dietary metal uptake; intestine

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