Influence of genetic polymorphisms in the β2-adrenoceptor on desensitization in human lung mast cells

The beta-adrenoceptor agonist, isoprenaline, inhibited the immunoglobulin E-mediated release of histamine from human lung mast cells (HLMC), Long-term (24 h) exposure of HLMC to isoprenaline reduced the subsequent effectiveness of isoprenaline to inhibit histamine release. The extent of this functional desensitization was variable with some HLMC preparations resistant and others highly susceptible. We sought to determine whether the variability in the degree of functional desensitization was influenced by genetic polymorphisms in the beta(2)-adrenoceptor. HLMC preparations were genotyped at two polymorphic loci, positions 16 (arg to gly) and 27 (gln to glu), and the effect of desensitizing conditions (24 h with 10(-6) M isoprenaline) on the subsequent ability of isoprenaline (10(-7) M) to inhibit histamine release from HLMC was determined (n = 72), In HLMC preparations expressing beta(2)-adrenoceptors with arg (wild-type) or gly (mutant) at position 16, desensitization was 71 +/- 5% (n = 18) or 43 +/- 5% (n = 26), respectively, whereas the desensitization was 59 +/- 6% (n = 28) for heterozygotes at this position, In HLMC preparations expressing beta(2)-adrenoceptors with gin (wild-type) or gill (mutant) at position 27, desensitization was 65 +/- 5% (n = 25) or 28 +/- 7% (n = 17), respectively, whereas the desensitization was 61 +/- 5% (n = 30) for heterozygotes at this position. These data suggest that mutant (gly(16) and glu(27)) forms of the receptor are resistant to desensitization compared to wild-type (arg(16) and gln(27)) forms. However, analyses to determine the relative contributions of positions 16 and 27 suggest that position 27 is more important in influencing the degree of functional desensitization. Pharmacogenetics 10:153-162 (C) 2000 Lippincott Williams & Wilkins.