Abstract
Halenaquinol, a natural cardioactive pentacyclic hydroquinone from the sponge Petrosia seriata, was found to be a powerful inhibitor of the rat brainstem and of the rat brain cortex Na+, K(+)-ATPases and the rabbit muscle sarcoplasmic reticulum Ca(2+)-ATPase with I50 values of 7.0 x 10(-7), 1.3 x 10(-6) and 2.5 x 10(-6) M, respectively. Halenaquinol also inhibited K(+)-phosphatase activity of the rat brain cortex Na+, K(+)-ATPase with an I50 value of 3 x 10(-6) M. Ouabain-insensitive Mg(2+)-ATPase activity of the microsomal fraction of the rat brain cortex was weakly inhibited by halenaquinol. Inhibition was irreversible, dose- and time-dependent. Naphthohydroquinone fragment in structures of halenaquinol, related natural and model compounds was very important for an inhibiting effect.
MeSH terms
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Adenosine Triphosphatases / antagonists & inhibitors*
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Animals
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Benz(a)Anthracenes / chemistry*
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Benz(a)Anthracenes / pharmacology*
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Brain Stem / enzymology
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Ca(2+) Mg(2+)-ATPase / antagonists & inhibitors
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Calcium-Transporting ATPases / antagonists & inhibitors
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Cell Membrane / enzymology
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Cerebral Cortex / enzymology
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Enzyme Inhibitors / pharmacology*
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Humans
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Myocardial Contraction / drug effects
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Phosphoric Monoester Hydrolases / antagonists & inhibitors
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Porifera / chemistry*
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Rabbits
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Rana ridibunda
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Rats
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Sarcoplasmic Reticulum / enzymology
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Sodium-Potassium-Exchanging ATPase / antagonists & inhibitors
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Structure-Activity Relationship
Substances
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Benz(a)Anthracenes
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Enzyme Inhibitors
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halenaquinol sulfate
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Phosphoric Monoester Hydrolases
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Adenosine Triphosphatases
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Ca(2+) Mg(2+)-ATPase
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Calcium-Transporting ATPases
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Sodium-Potassium-Exchanging ATPase