RYANODINE-SENSITIVE CALCIUM-RELEASE CHANNEL FROM LEFT-VENTRICLE, SEPTUM, AND ATRIUM OF CANINE HEART

Objective: The aim was to consider the possibility that functionally distinct forms of the ryanodine sensitive calcium release channel are expressed in different regions of heart. Methods: Membranous fractions enriched in ryanodine binding activity were isolated from canine left ventricular free wall, interventricular septum, and atrium. Ryanodine receptors (RyR) were purified by sucrose density gradient centrifugation, following solubilisation of sarcoplasmic reticular membranes with the detergent Chaps. Single channel currents were measured, upon reconstitution of sarcoplasmic reticular vesicles and the purified RyR into planar lipid bilayers. Results: Ryanodine sensitive Ca2+ release channels from three different regions of canine heart displayed the same [H-3]ryanodine binding and single channel characteristics. Conclusions: The left ventricular free wall, septum, and atrium of canine heart may express functionally related, if not identical, ryanodine receptor/Ca2+ release channels.