Are cardiac muscle cells ‘skinned’ by EGTA or EDTA?

Abstract

KNOWLEDGE of the processes involved in the contraction of skeletal muscle fibres has been greatly advanced by study of the ‘skinned’ fibre preparation. Here the sarcolemma is peeled off, giving access to the intracellular organelles unhampered by an intervening cell membrane. The small size of cardiac muscle cells had seemed to preclude the use of this technique, and so interest has been shown in a ‘chemical’ method for ‘skinning’ heart cells, which involves exposing the muscle to EGTA and EDTA (ref. 1). However, this paper questions the effectiveness of the EDTA/EGTA skinning methods, reporting that tension production in fully treated cells is [Na]_o dependent, and that the cells can support resting and action potentials in low [K]_o-‘skinning’ media. It is concluded that both the high Ca-sensitivity and low membrane potential of EGTA/EDTA-treated cells occur without radical impairment of the sarcolemmal permeability barrier. An alternative explanation for the high sensitivity to extracellular calcium is presented which involves the Ca–Na exchange mechanism.