The aim of this study was to identify the extent of genetic variability in breast cancer resistance protein (BCRP) in humans. We first analysed the sequence of BCRP cDNA from human livers and from human intestines phenotyped for expression of intestinal BCRP. We then determined the frequency of all known coding single nucleotide polymorphisms (cSNPs) using DNA from individuals representing 11 different ethnic populations. Nine SNPs including four non-synonymous and three synonymous cSNPs and two intronic SNPs were identified. Of the missense mutations, exon 2 SNP (G34A) resulted in a V12M change; exon 5 SNP (C421A) resulted in a Q141K substitution; exon 6 SNP (A616C) resulted in an I206L amino acid substitution; and exon 15 SNP (A1768T) resulted in a N590Y change in the BCRP protein. The two most frequent polymorphisms identified in the human population studied were the G34A and C421A transitions. There was marked variation in BCRP genotypes and allele frequencies in the different populations. BCRP mRNA was phenotyped in human small bowel intestinal samples by real-time polymerase chain reaction and BCRP protein was analysed on immunoblots of tissue from the same individuals. There was a 78-fold variation in expression of BCRP mRNA and significant variation in BCRP protein expression in human intestine. Expression of intestinal BCRP mRNA and protein was not different between persons expressing the common Gln141 allele compared to the Lys141 allele. Thus, common natural allelic variants of BCRP have been identified, and did not influence interindividual variation in expression of BCRP mRNA in human intestine, but remain to be tested for their effect on BCRP function.

This study investigates developmental changes in mRNA expression of seven SLC transporters including SLCO1B1, SLCO1B3, SLCO2B1, SLCO4A1, SLC22A7, SLC22A1, and SLC10A1 in human pediatric liver. It is hypothesized that expression of these genes undergoes developmental changes during the early years of life. Sixty‐one human pediatric liver samples were collected from living donors aged 0.3 to 12 years through liver biopsy. Real‐time RT‐PCR was used to quantify mRNA expression relative to cyclophilin for all target transporters. One‐way ANOVA with post hoc pairwise comparisons was performed to assess statistical differences in expression amongst different age groups (A: 0.3–0.7, B: 0.7–2, C: 2–5, D: 5–12 yrs). Mean normalized relative mRNA expression is presented in the table (bold figures indicate statistical significance (p<0.05)). It is concluded that in human pediatric liver, there are significant age‐dependent differences in mRNA expression of SLCO1B3 (OATP‐8) and SLCO4A1 (OATP‐E). Clinical Pharmacology & Therapeutics (2005) 77, P95–P95; doi: A(n = 9) B (n = 19) C (n = 12) D (n = 21) SLCO1B11928720353703771SLCO1B320.774.168.858.8SLCO2B10.160.400.450.52SLCO4A10.0030.0090.0140.015SLC22A71.654.234.173.31SLC22A16.1710.912.016.0SLC10A128.035.720.925.4