Solubilization and affinity labeling of a dihydropyridine binding site from skeletal muscle: effects of temperature and diltiazem on [3H]dihydropyridine binding to transverse tubules.

Effects of temperature and d-cis-diltiazem (DTZ) on [3H]nitrendipine (NTD) and [3H]nimodipine (NIM) binding to skeletal muscle t-tubular membranes were studied. A decrease in temperature from 37 degrees C to 10 degrees C decreased KD and increased Bmax slightly. DTZ increased binding by increasing Bmax under all conditions and also decreased KD for NTD at 37 degrees C. The binding protein labeled with [3H]isothiocyanate dihydropyridine revealed a molecular weight of 36,000. The binding site for NTD was solubilized by deoxycholate and dihydropyridine binding was still stimulated by DTZ in the solubilized form.