Separation and characteristics of inside-out and right side-out vesicles from a rat cardiac sarcolemma preparation

Purified cardiac sarcolemma (SL) vesicles are highly suitable to study various Ca2+-transport systems present in the SL. We describe in this paper the separation of the Inside-Out (IO) and Right side-Out (RO) oriented vesicle subpopulations from a purified rat heart SL preparation. The isolated subfractions were characterized with respect to the number of beta-adrenergic binding sites and the Ca2+-uptake and (Ca2+-Mg2+)-ATPase activities. It was found that the Ca2+-uptake and the (Ca2+-Mg2+)-ATPase activities reside in the IO fraction and are virtually absent in the RO fraction, confirming that the active Ca2+-uptake represents the outward directed sarcolemmal Ca2+-flux.