Inhibition of membrane transport ATPases by halenaquinol, a natural cardioactive pentacyclic hydroquinone from the sponge Petrosia seriata

Halenaquinol, a natural cardioactive pentacyclic hydroquinone from the spon ge Petrosia seriata, was found to be a powerful inhibitor of the rat brains tem and of the rat brain cortex Na+, K+-ATPases and the rabbit muscle sarco plasmic reticulum Ca2+-ATPase with I-50 values of 7.0 x 10(-7), 1.3 x 10(-6 ) and 2.5 x 10(-6) M, respectively. Halenaquinol also inhibited K+-phosphat ase activity of the rat brain cortex Na+, K+-ATPase with an I-50 value of 3 x 10(-6) M. Ouabain-insensitive Mg2+-ATPase activity of the microsomal fra ction of the rat brain cortex was weakly inhibited by halenaquinol. Inhibit ion was irreversible, dose- and time-dependent. Naphthohydroquinone fragmen t in structures of halenaquinol, related natural and model compounds was ve ry important for an inhibiting effect. (C) 1999 Elsevier Science Inc. All r ights reserved.