Determination of pollutants with multixenobiotic-resistance inhibiting properties

Recent evidence indicates that inherent presence of multixenobiotic resistance (MXR) mechanism represents a general biological defence mechanism for protection of organisms against both endogenous and environmental toxins. In aquatic organisms exposed to polluted waters, this P-170 glycoprotein pump also removes ‘new’ man-made toxic chemicals out of cells. Many chemical agents may alter the function of this fragile mechanism. A new class of compounds, referred to as ‘chemosensitizers’, deserve a top rank among environmentally-hazardous chemicals, since they block this basic natural defence mechanism. The authors measured the concentration of such MXR-inhibiting substances by two methods: the ‘binding’ assay and the ‘efflux’ assay. The ‘efflux’ assay of water from the polluted Sava and Rhein Rivers and the unpolluted Korona River revealed the presence of 440, 489, and 176 ppb of verapamil equivalents of MXR-inhibitors, respectively. These concentrations of MXR-inhibitors obviously may revert the natural resistance of organisms inhabiting these rivers to a pathobiologic sensitivity.