title: Differences in the intracellular accumulation of HIV protease inhibitors in vitro and the effect of active transport.
abstract: OBJECTIVE
  To investigate the intracellular accumulation of HIV protease inhibitors (PI) and to assess the effect of active transport on this accumulation.
  
  
  METHODS
  CEM cells were incubated with a PI for 18 h and the intracellular concentration determined using cell number and radioactivity. The effect of active transport was investigated using cells expressing P-glycoprotein (CEM(VBL)) and cells expressing multidrug resistance-associated protein 1 (MRP1; CEM(E1000)). Incubations were also carried out at 4 degrees C and in the presence of 2-deoxyglucose plus rotenone to examine the effect of inhibiting active transport.
  
  
  RESULTS
  Nelfinavir (NFV) accumulated to the greatest extent (> 80-fold) followed by saquinavir (SQV; approximately 30-fold), ritonavir (RTV; 3-7-fold) and finally indinavir (IDV; extracellular equivalent to intracellular). In CEM(VBL) cells there was a significant reduction in the intracellular accumulation of NFV, SQV and RTV and in CEM(E1000) cells there was reduced accumulation of SQV and RTV. Inhibition of active transport processes caused a reduction in SQV and RTV accumulation but had no effect on IDV accumulation in all cell types. NFV accumulation was increased in CEM(VBL) cells as a result of inhibition of active transport.
  
  
  CONCLUSIONS
  Marked differences can be detected in the intracellular accumulation of HIV PI drugs in vitro. Both P-glycoprotein and MRP1 may play a role in limiting the intracellular concentration of the PI and active influx mechanisms may contribute to drug accumulation.
authors.affiliation: Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, UK.
authors.forename: K
authors.initials: K
authors.lastname: Jones
authors.forename: P G
authors.initials: PG
authors.lastname: Hoggard
authors.forename: S D
authors.initials: SD
authors.lastname: Sales
authors.forename: S
authors.initials: S
authors.lastname: Khoo
authors.forename: R
authors.initials: R
authors.lastname: Davey
authors.forename: D J
authors.initials: DJ
authors.lastname: Back
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D001693:Biological Transport, Active; D002460:Cell Line; D017320:HIV Protease Inhibitors / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D019469:Indinavir / Q000378:metabolism; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D019888:Nelfinavir / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019438:Ritonavir / Q000378:metabolism; D019258:Saquinavir / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D017320:HIV Protease Inhibitors; D019469:Indinavir; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D019888:Nelfinavir; D019438:Ritonavir; D019258:Saquinavir