engleski

Multixenobiotic resistance mechanism in honeybees

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, similar to the well-known multidrug resistance (MDR) phenomenon involved in tumor cell lines resistant to chemotherapeutic drugs, is mediated by the energy dependent activity of the transmebrane P-glycoprotein (Pgp). Pgp pumps out of cells and organisms a wide variety of xenobiotics, including man-made, as well as natural chemicals, preventing their accumulation and toxic behavior. This property classifies MXR among the first line defence mechanisms. However, this mechanism is fragile - many chemical agents my act as MXR inhibitors MXR mechanism is inducible. The natural level of MXR activity may be very different in different populations. Consequently, the resistance of various populations of the same species to the same agent (or parasites) may be very different, according to the level of MXR induction. MDR/MXR-like genes or phenotypes have been identified in a broad spectrum of taxons. Such broad distribution suggests its general biological defence function. Regard these facts the aim of our experiment was to investigate do the honeybees also have MXR 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. Our preliminary results showed that honeybees accumulate 17 - 88% more RB in the presence of VER and 95 - 150% more RB when CA was used as a model MXR inhibitor, respectively. These observations presents the first evidence that MXR mechanism also could be present in honeybees.

honeybee; multixenobiotic resistance

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