Relationship of β-adrenoreceptor density to fitness in athletes

Abstract

Physical training in man results in a decreased heart rate at rest^1,2, associated with an apparent decrease in the activity of the sympathetic nervous system^1,3. One possible mechanism for this would be alterations in β-adrenoreceptor density with training. Exercise produces large increases in plasma catecholamine concentrations^4,5. Moreover, lymphocyte β-adrenoreceptor density in man is inversely correlated with plasma and urinary noradrenaline concentrations and is positively correlated with cardiac sensitivity to isoprenaline⁶. Thus, alterations in β-adrenoreceptor density in the cardiovascular system might be reflected in changes in lymphocyte β-adrenoreceptor density. We have now measured lymphocyte β-adrenoreceptor density in a group of athletes of varying degrees of fitness before and after they embarked on an intensive training programme. Our results show clear correlations between degree of physical fitness and receptor density and we conclude that decreases in sympathetic nervous system responsiveness following physical training are related to decreases in β-adrenoreceptor density.