β-Adrenergic receptor number in human lymphocytes is inversely correlated with aerobic capacity

In the present study, the relationships between beta-adrenergic receptor (beta-AR) expression and aerobic capacity evaluated by maximal oxygen consumption (V(over dot)O-2max) and oxygen consumption level at ventilatory threshold (V(over dot)O-2@VT) were investigated. Seventeen physically untrained and 25 trained men participated in the study. After supine resting, the peripheral blood was sampled for preparation of lymphocytes, the model cell used to analyze the beta-AR state. The total number of beta-AR in lymphocytes (beta-AR(total)) was inversely correlated with the V(over dot)O-2max (r = -0.368; P < 0.05) and the V(over dot)O-2@VT (r = -0.359; P < 0.05). Similar relationships were also observed between the number of beta-AR in cell surface and both V(over dot)O-2max (r = -0.491; P < 0.05) and V(over dotO(2)@VT (r = -0.498; P < 0.05). However, no correlation was obtained between the number of beta-AR in intracellular compartments and either V(over dot)O-2max or V(over dot)O-2@VT. The beta(2)-AR mRNA level quantified by the use of competitive reverse transcription-polymerase chain reaction was inversely correlated with V(over dot)O-2@VT (r = -0.567; P < 0.05) and positively correlated with beta-AR(total) (r = 0.521; P < 0.05). These findings suggest that the beta-AR number in lymphocytes is inversely correlated with aerobic capacity. This relationship may be explained by downregulation of beta-AR, including internalization with subsequent degradation of the receptors and inhibition of the beta-AR biosynthesis.