MDR1 haplotypes significantly minimize intracellular uptake and transcellular P-gp substrate transport in recombinant LLC-PK1 cells

J Pharm Sci. 2006 Oct;95(10):2293-308. doi: 10.1002/jps.20717.


To date, research on the effect of single nucleotide polymorphisms (SNPs) on P-glycoprotein (P-gp) expression and functionality has rendered inconsistent results. This study systematically evaluates the impact of MDR1 haplotypes (1236/2677, 1236/3435, 2677/3435, 1236/2677/3435) on P-gp functionality compared to individual SNPs (1236, 2677, and 3435) in validated stable recombinant epithelial cells. Recombinant LLC-PK1 cells expressing MDR1wt or its variants were developed and validated for this purpose. Intracellular accumulation and time-dependant efflux of a P-gp substrate, Rhodamine 123 (R123, 5 microM) were evaluated in control and recombinant cells. Additionally, the transepithelial transport of R123 (1 microM) and Vinca alkaloids (5 microM) was evaluated. Except for MDR1(2677T) and MDR1(1236T/2677T/3435T), cells expressing MDR1 variants displayed intermediate R123 intracellular accumulation (1.5-2-fold higher) and lower effluxed R123 (10-20% vs. 52%) compared to those expressing MDR1wt. Efflux ratios across MDR1wt expressing cells were significantly larger for R123 (3.95+/-1.1), Vinblastine (3.75+/-0.26), and Vincristine (2.8+/-0.29). Recombinant cells expressing MDR1 variants displayed 0%-22.7% P-gp activity (approximately 80%-100% efflux loss). Results suggest that MDR1 polymorphisms at the 1236, 2677, and/or 3435 positions significantly minimize P-gp functionality in vitro, the extent of which appears to be substrate dependant.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism*
  • Animals
  • Biological Transport
  • Fluorescent Dyes / metabolism
  • Gene Expression
  • Genes, MDR / genetics*
  • Haplotypes
  • LLC-PK1 Cells
  • Polymorphism, Single Nucleotide
  • Rhodamine 123 / metabolism
  • Swine
  • Transfection
  • Vinblastine / metabolism
  • Vincristine / metabolism


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Fluorescent Dyes
  • Rhodamine 123
  • Vincristine
  • Vinblastine