Inhibition of the erythrocyte Na+, K+-pump by mammalian lignans

Several mammalian lignans, particularly enterolactone, 3-oxy-methyl enterolactone and prestegane B are able to inhibit Na+, K+-pump activity in human red cells with IC50 of about 1 mM. The inhibition of Na+, K+-pump activity by mammalian lignans have the following properties: the IC50 for ouabain remains unchanged suggesting a noncompetitive inhibition. The apparent affinity for internal Na+ and maximal rate of cation translocation are both diminished. The above inhibition of the Na+, K+-pump was obtained at doses 2-3 orders of magnitude higher than those required for ouabain. However we cannot exclude that a glycosyl- (and/or butenolide)-derivative of enterolactone could be one endogenous ouabain-like factor.