the positive inotropic effect may be explained by a ouabain-induced conformational alteration of the na-k-atpase which leads to structural alterations of the plasmalemma connected with an increased availability of coupling calcium.4 increasing the frequency of stimulation over a critical value , which appears to be determined by an overloading of the na pump , induces a decrease in contractile force , cellular accumulation of na and loss of k , and eventually contracture.5 the rate of binding of ouabain appears to depend on the actual concentration of particular conformations of the na-k-atpase with high affinity for ouabain .
C0007603
plasmalemma
C0007634
cellular