Influence of β1 -adrenoceptor polymorphisms on the expression of β1 -adrenoceptors in human lung tissue

L.J. Kay1, S.K. Suvarna2, R. Chess-Williams3 and P.T. Peachell1. 1Academic Unit of Clinical Pharmacology, University of Sheffield. 2Histopathology, Northern General Hospital, Sheffield. 3Faculty of Health Sciences and Medicine, Bond University, Queensland, Australia.

Human lung tissue contains both β2 - and β1 -adrenoceptors at a reported ratio of 4:1 (Sano et al., 1993). However, previous work within our group has shown extensive variability in the expression of β-adrenoceptors in human lung. The possibility that genetic polymorphisms in β-adrenoceptor genes might influence receptor expression has been explored. A statistically significant (P<0.05) association between a single nucleotide polymorphism (SNP) in the β2-adrenoceptor gene (491 C>T) and β2-adrenoceptor expression has been observed in human lung tissue (data unpublished). The aim of the present study was to determine whether a similar association might exist between two common SNPs (145 A>G (Ser49Gly) and 1165 C>G (Arg389Gly)) in the β1-adrenoceptor gene and β1-adrenoceptor expression.

Human lung tissue (n=78) was obtained from surgical resections. Saturation binding assays using 125I-iodocyanopindolol (0.0156 - 2 nM) were performed on membrane fractions of lung tissue and specific binding assessed using methods that have been described (Nishikawa et al., 1996). Discrimination of β2 - and β1 -adrenoceptors was determined using the selective β1-adrenoceptor antagonist, CGP20712A (0.01μM). For genotypic analysis, genomic DNA was extracted from a small amount of human lung tissue, and genotype determined by PCR-RFLP using the restriction enzymes Eco0109I (145 A>G) or BsmFI (1165 C>G). Data were analysed using GraphPad Prism software. Statistical significance was determined using either Mann-Whitney or Kruskal-Wallis tests.

In human lung tissue (n=78), β1-adrenoceptor densities ranged from 0 to 46 fmol mg-1 protein (mean ± s.e.m; 8 ± 1 fmol mg-1 protein). All 78 preparations were genotyped at positions 145 and 1165 of the β1-adrenoceptor gene. Both SNPs where shown to be in Hardy-Weinberg equilibrium, as evaluated by χ2 goodness of-fit-tests. Since only 2 preparations were found to express the less common allele at position 145, these data were not included in the statistical analysis. Neither position 145 A>G, nor 1165 C>G appeared to influence β1 -adrenoceptor density (P>0.05; see table 1).

Table 1 Nucleotide position

To conclude, preliminary findings suggest that, although there is extensive inter-individual variability in β1 -adrenoceptor densities in lung, this is not influenced by SNPs 145 A>G or 1165 C>G of the β1 -adrenoceptor gene.

Nishikawa, et al., (1996). Eur J Pharmacol, 318,123-129
Sano, et al., (1993). Life Sciences, 52, 1063-70