Single-channel activity in sarcolemmal vesicles from human and other mammalian muscles.

Segments of mammalian, including human, skeletal muscle 1-2 cm long can be induced to shed vesicles by treatment with collagenase in a high-KCl solution containing no added calcium. The vesicles are encompassed by clean sarcolemma so that the gigaseal necessary for patch-clamping is readily formed. The properties of inwardly rectifying potassium channels and of calcium-activated potassium channels in patches detached from such vesicles are shown to be consistent with expectations based on earlier studies on intact muscle fibers and with patch clamp results on the same type of channels in other tissues. A chloride channel which rectifies outwardly with a conductance ranging from 15 to 50 pS is also described. The utility of sarcolemmal vesicles for the study of ion channels in human biopsy material is discussed.