Effect of ginseng saponin on the Na+, K+-ATPase of dog cardiac sarcolemma

Abstract

The effects of ginseng saponins on the sarcolemmal Na,+ K+-ATPase were compared to gypsophila saponin, sodium dodecylsulfate (SDS), and Triton X-100 to elucidate whether the effects are due to the membrane disruption, using a highly enriched preparation of cardiac sarcolemma prepared from dog ventricular myocardium. About 26% and 29% of vesicles in the preparation, enriched in ouabain-sensitive Na,+ K+-ATPase, β-adrenergic and muscarinic receptors are rightside-out and inside-out in orientaton, respectively. Ginseng saponins (triol>total>diol) inhibited Na+, K+-ATPase activity, Na+-dependent phosphorylation and [3H]ouabain binding of sarcolemmal vesicles. However, gypsophila saponin, SDS (0.4μg/μg protein) and Triton X-100 (0.6μg/μg protein) caused about 1.35 and 1.40-fold increase in Na+, K+-ATPase activity and [3H] ouabain binding, respectively. Especially, the activating effect of gypsophila saponin on membrane Na+, K+-ATPase was detected at gypsophila saponin to sarcolemmal protein ratios as high as 100. Low dose of ginseng saponin (3μg/μg protein) decreased the phosphorylation sites and the concentration of ouabain binding sites (Bmax) without affecting the turnover number and affinity for ouabain binding, while gypsophila saponin, SDS (0.4ug/ug protein), and Triton X-100 (0.6μg/μg protein) increased the Bmax. The results suggest that ginseng saponins cause a decrease in the number of active sites by interacting directly with Na+, K+-ATPase before disruption of membrane barriers of sarcolemmal vesicles.