Influence of receptor polymorphisms on the response to alpha-adrenergic receptor blockers in pheochromocytoma patients

Background: Presurgical treatment with an alpha-adrenergic receptor blocker is recommended to antagonize the catecholamine-induced alpha-adrenergic receptor mediated vasoconstriction in patients with pheochromocytoma or sympathetic paraganglioma (PPGL). There is, however, a considerable interindividual variation in the dose-response relationship regarding the magnitude of blood pressure reduction or the occurrence of side effects. We hypothesized that genetically determined differences in alpha-adrenergic receptor activity contribute to this variability in dose-response relationship. Methods: Thirty-one single-nucleotide polymorphisms (SNPs) of the alpha 1A, alpha 1B, alpha 1D adrenoreceptor (ADRA1A, ADRA1B, ADRA1D) and alpha 2A, alpha 2B adrenoreceptor (ADRA2A, ADRA2B) genes were genotyped in a group of 116 participants of the PRESCRIPT study. Haplotypes were constructed after determining linkage disequilibrium blocks. Results: The ADRA1B SNP rs10515807 and the ADRA2A SNPs rs553668/rs521674 were associated with higher dosages of alpha-adrenergic receptor blocker (p < 0.05) and with a higher occurrence of side effects (rs10515807) (p = 0.005). Similar associations were found for haplotype block 6, which is predominantly defined by rs10515807. Conclusions: This study suggests that genetic variability of alpha-adrenergic receptor genes might be associated with the clinically observed variation in beneficial and adverse therapeutic drug responses to alpha-adrenergic receptor blockers. Further studies in larger cohorts are needed to confirm our observations.