Relative quantification of beta-adrenergic receptor in peripheral blood cells using flow cytometry.

Beta-adrenergic receptors (β-ARs) play a critical role in many diseases. Quantification of β-AR density may have clinical implications in terms of assessing disease severity and identifying patients who could potentially benefit from beta-blocker therapy. Classical methods for β-AR quantification are based on labor-intensive and time-consuming radioligand binding assays. Here, we report optimization of a flow cytometry-based method utilizing a biotinylated β-AR ligand alprenolol as a probe and use of this method to quantify relative receptor expression in healthy controls (HC). Quantum™ MESF beads were used for quantification in absolute fluorescence units. The probe was chemically modified by adding a spacer moiety between biotin and alprenolol to stabilize receptor binding, thus preventing binding decay. Testing of three different standard cell fixation and permeabilization methods (formaldehyde fixation and saponin, Tween-20, or Triton-X 100 permeabilization) showed that the formaldehyde/Triton-X 100 method yielded the best results. β-AR expression was significantly higher in granulocytes compared to mononuclear cells. These data show that flow cytometric quantification of relative β-AR expression in circulating leukocytes is a suitable technology for large-scale clinical application.