Dihydropyridine sites separate from junctional sacroplasmic reticulum in hypertension

Distribution patterns on linear sucrose gradients for dihydropyridine (DHP) binding sites and Mr 300K polypeptides marker for junctional sarcoplasmic reticulum were determined in left ventricular microsomes of control and chronically pressure-overloaded cat hearts. Major peak of DHP sites corresponded in position and shape to distribution of Mr 300K polypeptide in controls but appeared at a lighter buoyant density in hypertrophy, similar to junctional plasma membrane (T-tubules) isolated from normal microsomes by French press treatment of dyad fraction.