Influence of genetic polymorphisms on intestinal expression and rifampicin-type induction of ABCC2 and on bioavailability of talinolol

Objectives To evaluate whether ABCC2 gene polymorphisms are associated with expression and/or function of the efflux pump. Methods We investigated the allele frequency of ABCC2 -24C > T, -23G > A, c.1 249G > A, c.1446C > G, c.1457C>T, c.2302C>T, c.2366C>T, c.3542G>T, c.3561G>A, c.3563T>A, c.3972C>T, c.4348G>A, and 4544G>A in 374 nonrelated German healthy volunteers and determined the impact on duodenal mRNA and protein content of ABCC2. For functional analysis, the disposition of intravenously (30 mg) and orally administered talinolol (100 mg) was measured among 31 individuals. Moreover, the effects of rifampicin-type induction (600 mg, 8 days) of duodenal ABCC2 were quantified in 22 participants with regard to genetic polymorphisms. Results The allele frequencies were 18.3% (-24T), 21.1% (1249A), 1.4% (1446G), 0.1 % (3542T), 4.5% (3563A), 34.2% (3972T), and 4.4% (4544A); carriers of -23G > A, 1457C > T, 2302C > T, 2366C > T, 3561 G > A, and 4348G > A were not identified. The -24T allele was in strong linkage with 3972T, and 3563A with 4544A, whereas 1249A was weakly linked with other variant alleles. None of the single nucleotide polymorphisms investigated influenced significantly intestinal ABCC2 mRNA and protein content. The variant ABCC2 1249G >A (V4170, however, was associated with lower oral bioavailability (P=0.001), and increased residual clearance of intravenous talinolol (P=0.021). Intestinal ABCC2 mRNA and protein expression were upregulated by rifampicin treatment, a genetic influence could be detected in only four cases heterozygote for 3563T>A or 4544G >A. Conclusion The 1249G>A (V4171) polymorphism is obviously associated with higher activity of the intestinal transporter.