Abstract
1 In order to understand tissue-specific differences in sensitivity to ouabain, the distribution of [3H]-ouabain was investigated in seven functionally different, canine cardiac tissues. 2 Specialized cardiac tissues (e.g., pacemaker or conducting tissues) accumulate much less ouabain than do the contractile tissues such as the left ventricle or the papillary muscle. 3 This study confirms a greater Rb+ uptake in the Purkinje fibre than in the contractile tissue. 4 The results disprove the hypothesis that a high accumulation of ouabain in the Purkinje fibre is responsible for the well-known sensitivity to ouabain in this tissue.