The inhibitory adenylate cyclase coupling protein in pseudohypoparathyroidism.

Deficient activity of the adenylate cyclase stimulatory coupling protein (Ns) has been demonstrated in many patients with pseudohypoparathyroidism type I (PHP) who have Albright's hereditary osteodystrophy and multiple hormone resistance. Since an abnormality in the activity of the related adenylate cyclase inhibitory coupling protein (Ni) could influence hormone responsiveness, we measured pertussis toxin-catalyzed [32P]ADP ribosylation of the 40,000-dalton alpha-subunit of Ni (Ni alpha) in erythrocyte membranes from patients with PHP and normal subjects. There were no significant differences in the amounts of Ni alpha in membranes from normal subjects, patients with PHP who have low Ns associated with Albright's hereditary osteodystrophy and multiple hormone resistance, and patients with PHP who have normal Ns. Abnormal Ni is not likely to cause hormone resistance in patients with PHP who have normal Ns or to influence hormone responsiveness in patients with PHP who have low Ns.