Expression of MDR1, MRP2 and BCRP mRNA in tissues of turkeys.

MDR1, MRP2 and BCRP are members of the superfamily of ABC membrane transporters that export a large variety of structurally diverse substances out of the cell, hence being an integral part of various biological barriers. Here we report for the first time the tissue distribution of these ABC efflux transporters in the gastrointestinal tract (crop, proventriculus, duodenum, proximal and distal jejunum, ileum, caecum, colon) as well as in liver, kidney, lung, brain, adrenal gland, ovaries, oviduct and testes in BUT9 turkeys. MDR1 and BCRP mRNA expression was detected in all tissue samples, and the highest levels were measured in the small intestines. The tissue distribution of MRP2 mRNA was less consistent and some tissues seemed to lack any significant expression. Moreover, in consideration of previous findings suggesting that fluoroquinolones are substrates and modulators of ABC transporters, the effect of orally administered danofloxacin mesylate on the levels of MDR1, MRP2 and BCRP mRNA expression was investigated. Danofloxacin treatment resulted in a significant up-regulation of the measured transporters at the transcriptional level in the upper part of gastro-intestinal tract, liver and kidneys as well as in barrier-protected organs, such as the brain. However, despite this significant increase in the transcription levels, the pharmacokinetic parameters after repeated application of danofloxacin mesylate were not significantly altered.