[H-3] NITRENDIPINE RECEPTORS AS MARKERS OF A CLASS OF PUTATIVE VOLTAGE-SENSITIVE CA2+ CHANNELS IN NORMAL HUMAN SKELETAL-MUSCLE AND IN MUSCLE FROM DUCHENNE MUSCULAR-DYSTROPHY PATIENTS

Properties of nitrendipine receptors have been analyzed in skeletal muscle from normal young boys and boys with Duchenne muscular dystrophy (DMD). The dissociation constant (Kd) of the complex formed by nitrendipine with its specific receptors was 0.5 .+-. 0.1 nM in dystrophic muscle and 0.4 .+-. 0.1 nM in normal muscle. Maximum binding capacities Bmax were 403 .+-. 80 and 460 .+-. 60 fmol/mg protein in DMD and normal muscle, respectively. These results suggest that nitrendipine binding sites on nitrendipine-sensitive Ca2+ channel binding sites are not altered in Duchenne muscular dystrophy.