s presenting different electron densities in the heme aggregate found in the central area of the organelle, 7 / 20 ABC-Mediated Heme and Pesticide Detoxification Fig 1. Uptake of Rhodamine 123 by midgut digest cells. Digest cells from fully engorged adult females were obtained as described in the Methods. Digest cells were incubated in the presence of 0.5 M Rhodamine 123 for 4 h. Control; cells preincubated with 10 M CsA. Panels are fluorescence images or differential interference contrast merged with fluorescence. Digestive vesicles labeled are indicated in the figure by white arrows. Scale bar is 40 m. Fluorescence intensity was measured in images from two independent experiments. Data shown are mean SEM. means p < 0.05. doi:10.1371/journal.pone.0134779.g001 Fig 2. Immunolocalization of ABC transporters in the tick midgut digest cell. Fully engorged females were dissected, fixed and included in paraffin. Deparaffinized sections were stained using polyclonal antibodies against an aminoterminal segment of human PgP-1 or rabbit non-immunized serum, followed by Alexa 633-labeled secondary antibodies. Images are DIC, fluorescence and DIC merged with fluorescence. Asterisk shows a labeled digestive vesicle. Arrow indicates a labeled digestive vesicle membrane. The scale bars is 40 m. doi:10.1371/journal.pone.0134779.g002 8 / 20 ABC-Mediated Heme and Pesticide Detoxification Fig 3. Identification of a CsA-sensitive ATPase activity in the hemosome membrane. Digest cells from fully engorged tick females 2 days after blood meal showing hemosome and digestive vesicle. Both hemosomes membranes and digestive vesicles membranes exhibit strong ATPase activity, as revealed by the precipitation of cerium phosphate; section from a distinct midgut diverticulum from the same tick, preincubated with 10 M CsA for 30 min before the ATPase assay. The scale bar is 200 nm or 100 nm. The images are representative of two independent experiments. doi:10.1371/journal.pone.0134779.g003 probably reflect the gradual increase in heme content that occurs during maturation of the organelle, as proposed PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19754877 by Lara et al. In a previous report, it was determined that an ABC transporter was involved in the detoxification of ivermectin and other acaricides. We therefore hypothesized that PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19758226 the presence of ABC transporters in the heme transport pathway that ends in the hemosome could also turn this organelle into a site for the get Relebactam disposal of other toxic compounds such as xenobiotics, in addition to its primary role as a site for the disposal of excess heme. As we had one R microplus isolate that was amitraz-sensitive, the POA strain and also an amitraz-resistant field isolate, we compared the uptake of Sn-Pp IX by digest cells from both strains to observe the relationship between amitraz resistance and heme detoxification by ABC transporters. After 2 h of incubation in medium with Sn-Pp IX, digest cells of the amitraz-resistant strain presented higher metalloporphyrin uptake than cells from the susceptible strain. Sn-Pp IX uptake was markedly inhibited by CsA, which reinforces the conclusion that ABC transporters are involved in this 
process. When cells were incubated with SnPp IX and the amount of SnPp IX in isolated hemosomes was evaluated by HPLC, organelles from the resistant strain also exhibited a higher level of accumulation. 9 / 20 ABC-Mediated Heme and Pesticide Detoxification Fig 4. CsA-sensitive uptake of Sn-Protoporphyrin IX is higher in amitraz-resistant ticks. Digest c