Trace elements and trace-element-containing proteins in the respiratory tract of the rat

摘要

Trace elements may have beneficial or harmful effects and both aspects have to be considered in the studies on their role in mammalian tissues. This applies to a special degree to the investigation of the metals and metalloids in the respiratory tract. The surface of the trachea and the lungs is continuously exposed to gases and particular matter present in the atmosphere. As many of these pollutants are powerful oxidants, theses tissues require a specific antioxidant defense system, Several enzymes with antioxidative functions are known to contain metals or metalloids as essential constituents of their active centers, and there may be further protective trace-element containing proteins not yet identified. However, metals and metalloids may also be incorporated accidentally from the aerosolic particular matter in forms and concentrations which may cause pathological changes. It is therefore of great interest to analyze the trace elements present in the respiratory tract and to obtain information on their subcellular distribution, their chemical forms and their biological effects. In studies carried out on rats element analytical methods and radiotracer techniques have been combined with biochemical separation procedures. Subcellular separation of the tissues into nuclear, mitochondrial, microsomal and cytosolic fraction has been achieved by differential ultracentrifugation. Instrumental neutron activation analysis (INAA) has been used to determine the concentration of several trace elements in the whole organ. After separation of the cytosolic proteins by size exclusion chromatography (SEC), inductively coupled plasma mass spectrometry (ICP-MS) has been employed to obtain first information on the trace element-containing proteins present in this compartment. The selenium-containing proteins in cytosolic fractions of the lung and the trachea have been investigated by labeling rats in vivo with ~(75)Se, gel electrophoretic separation of the proteins and autoradiographic detection of the tracer distribution.