A convenient method for measuring receptor-cyclase coupling activity in whole blood: application to Duchenne muscular dystrophy.

Activity of the guanine nucleotide-binding regulatory (N protein) component of adenylate cyclase can be measured in extracts of whole blood, using a modification of an assay previously applied to erythrocyte membranes. N protein activities in the blood of three patients with Duchenne muscular dystrophy and eight heterozygous carriers of the disease did not differ significantly from activities measured in blood of seven normal subjects. In contrast, the modified assay showed a 50% deficiency of N protein activity in blood of four patients with pseudohypoparathyroidism, type I, in whom erythrocyte studies had previously demonstrated a comparable degree of N deficiency.