In vivo assessment of xenobiotic transporter function in Apis mellifera.

Honeybees are an extremely important and vulnerable agricultural resource utilized worldwide. They are susceptible to sub-lethal effects from many chemicals that in conjunction with other toxins may have a lethal synergistic effect. One such synergistic effect is inhibition of ABC transporters, trans-membrane proteins found in many tissues of the honeybee that aid in effluxing many toxins from sensitive tissues. Development of an assay to quickly and reliably test if a chemical is an inhibitor of these transporter proteins is necessary to sort through and target potential candidates for more in depth studies with honeybees, including hive studies which are very time consuming. With this goal in mind an assay was developed in which rhodamine B, a known substrate of some key transporter proteins, is fed to honeybees and subsequently quantified in hemolymph gut and brain tissues.  Bees with compromised transporters are expected to have more rhodamine B in blood and brain tissues. As a test, bees were treated with verapamil, a known inhibitor of the ABCB family of transporters. Those bees pre-treated with 1mM verapamil+sucrose consistently had a higher level of dye in their blood than bees fed only sucrose syrup supporting the hypothesis that in vivo activity of some xenobiotic transporters can be measured using this fluorescent dye.