THE ACTIVITY OF MULTIXENOBIOTIC RESISTANCE MECHANISM DETERMINED BY RHODAMINE B-EFFLUX METHOD AS A BIOMARKER OF EXPOSURE

An important characteristic of multixenobiotic resistance (MXR) is its inducibility. The level of MXR-expression in field populations of aqu atic organisms is directly proportional to the level of pollution. Thi s property offered the possibility, to use the MXR-activity as a bioma rker of exposure. However, before application of MXR-activity as a rel evant biomarker, direct demonstration of the dynamic of MXR-activity, response to exposure to xenobiotics, as well as its response to cessat ion ofexposure, are required to make plausible that idea. For these re asons Me examined the dynamics of the rate of induction of MXR-activit y in marine mussel Mytilus galloprovincialis during either experimenta l exposure to seawater spiked with 1 mu M rhodamine 123 or with Diesel -2 oil (equivalent to 100 ppb of Kuwait oil), or in-the;field exposure to pollution. The rate of deinduction was followed infield-specimens during the recover;: period after their transfer from the polluted to the unpolluted site. The level of expression of MXR-transporter in the se experiments was assessed by measurement of the rate of accumulation , or. the rate of release, of rhodamine B. The induction of MXR-activi ty was completed within four days, and its deinduction was completed w ithin the same rime. However, despite this promptness in response, it remains to explore in future research whether the high natural level o f the MXR-activity, in combination with a relatively weak rate of indu ction allows its plausible use as a biomarker of exposure to xenobioti cs. (C) 1998 Elsevier Science Ltd. All rights reserved.