Abstract
We have used charged amphiphiles as phospholipid analogues to modulate the interaction of Ca2+ with myocardial sarcolemma. The amphiphiles were dodecyl sulfate, dodecyltrimethylamine, and lauryl acetate; these are anionic, cationic, and neutral molecules, respectively. The hydrophobic alkyl chain is identical in each case; only the hydrophilic head group is varied. The anionic dodecyl sulfate (50-100 microM) augmented the Ca2+ binding and Na+-Ca2+ exchange activity of sarcolemmal vesicles by approximately 80% and increases the contractility of rabbit papillary muscle. Both developed force and its derivative were increased by approximately 100% with no increase in rest tension. Cationic dodecyltrimethylamine (20-100 microM) produced nearly opposite effects. Neutral lauryl acetate (100 microM) had little apparent effect on any measurement. The charged amphiphiles should be useful tools for further elucidation of excitation-contraction coupling processes in a variety of contractile tissues.
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