engleski

Activity of multixenobiotic resistance mechanism in honeybees

A mechanism of multixenobiotic resistance (MXR) has been recently described in aquatic invertebrates. The function of MXR may explain a resistance of many aquatic organisms to toxic xenobiotics typically present in polluted waters. The molecular mechanism of MXR is similar to the well-known multidrug resistance (MDR) phenomenon involved in tumor cell lines resistant to chemotherapeutic drugs. MXR mechanism pumps out of cells and organisms all xenobiotics, including man-made, as well as natural chemicals, preventing their accumulation and toxic behavior. This property classifies MXR among defense mechanisms. The natural activity of MXR mechanism may be very different in different populations. Resistance of the same species to some agent may be very different, resulting in greater differences between populations exposed to chemicals and/or parasites. For the first time the presence of MXR mechanism in honey bee was presented on the 47th Annual Meeting of the Society of the German Bee Research Institutes from 3rd - 5th April 2000 in Blaubeuren, Germany. However, many chemical agents may inhibit the function of this mechanism. The presence and function of the MXR mechanism in honeybees were tested using methods of functional-activity measurements. We measured the potential of known MXR inhibitors Verapamil (VER) and Cyclosporin A (CA) to modulate (i.e. increase) the accumulation ratio of a fluorescent model MXR substrate Rhodamine B, in the midgut and rectum tissues of honeybees A. m. carnica previously exposed to high concentrations of RB in the presence or in the absence of MXR inhibitors. Functional activity measurements are shown on graph 1. Evidence of basal levels of MXR activity in different lines of bees was recognized (Graph 2). Difference betveen lines of honeybees expressed in average accumulation 7 – 111 % more RB when CA was used as a model MXR inhibitor.

honeybee; multixenobiotic resistance

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