AUTORADIOGRAPHIC VISUALIZATION OF BETA-ADRENERGIC RECEPTORS IN NORMAL AND DENERVATED SKELETAL-MUSCLE

Autoradiographic localization of β-adrenergic receptors in rat skeletal muscle in vivo was achieved utilizing [125I]-iodohydroxybenzylpindolol, a potent β-adrenergic blocker with high affinity and specificity for those receptors. In normal muscle the β-adrenergic receptors were localized mainly to blood vessels, arterioles>>venules, with much less concentration of grains over the fascicles of muscles fibers. One week after denervation there was an increase in binding both to blood vessels and muscle fibers, more so in soleus and gastrocnemius than in extensor digitorum longus. While these results parallel in vitro biochemical studies, they dictate caution when inferring cellular localization of β-adrenergic receptors (and other molecules) solely in the basis of biochemical techniques applied to subcellular fractions of whole-organ homogenates.