DETERMINATION OF POLLUTANTS WITH MULTIXENOBIOTIC RESISTANCE INHIBITING PROPERTIES

Recent evidence indicates that inherent presence of multixenobiotic re sistance (MXR) mechanism represents a general biological defence mecha nism for protection of organisms against both endogenous and environme ntal toxins. In aquatic organisms exposed to polluted waters, this P-1 70 glycoprotein pump also removes 'new' man-made toxic chemicals out o f cells. Many chemical agents may alter the function of this fragile m echanism. A new class of compounds, referred to as 'chemosensitizers', deserve a top rank among environmentally-hazardous chemicals, since t hey block this basic natural defence mechanism. The authors measured t he concentration of such MXR-inhibiting substances by two methods: the 'binding' assay and the 'efflux' assay. The 'efflux' assay of water f rom the polluted Sava and Rhein Rivers and the unpolluted Korana River revealed the presence of 440, 489, and 176 ppb of verapamil equivalen ts of MXR-inhibitors, respectively. These concentrations of MXR-inhibi tors obviously may revert the natural resistance of organisms inhabiti ng these rivers to a pathobiologic sensitivity.