Adrenergic receptor responses of vascular smooth muscle in Becker dystrophy. A muscle blood flow study using the 133Xe clearance method.

The effect of intravenous adrenaline and of alpha and beta blockade on muscle blood flow in the tibialis anterior muscle of 8 normal subjects and 8 patients with the Becker form of X-linked muscular dystrophy has been assessed using the 133Xe clearance method. Whereas beta receptor responses to stimulation by adrenaline and blocking by propranolol did not differ significantly in the Becker patients and normal controls, the degree of alpha receptor blockade produced by phentolamine was significantly less in the Becker patients, suggesting a quantitative or qualitative abnormality of vascular alpha receptors. This pattern of response was not found in patients with spinal muscular atrophy or polymyositis. The possible significance of these findings is considered.