INTERACTION OF ANTHRAQUINONES WITH NUCLEOTIDE-BINDING SITE OF NA-ATPASE(,K+)

The inhibitory effect of eight anthraquinone derivatives on the ATP hy drolytic activity of Na+, K+-ATPase from dog kidney was studied. The m agnitude of the inhibitory action of these substances was found to dep end on the apparent acid-base dissociation constant (pK(a)(app)). Name ly, when the pK(a)(app) values exceeded the level 7.1, the inhibitory actions of the respective anthraquinones steeply decreased. Additional ly, inhibitory effect of anthraquinones was found to be potentiated by the existence of triazine moiety in the molecule. The presence of the areas with ''high density of electrons'' in the anthraquinone molecul e (e.g. the sulfoethylsulfonyl chain in the molecule of Remazol Brilli ant Blue R) also potentiated their inhibitory action.