A comparative study between a brain Na+,K(+)-ATPase inhibitor (endobain E) and ascorbic acid |
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Authors: | Rodríguez de Lores Arnaiz G Herbin T Peña C |
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Affiliation: | (1) Instituto de Biología Celular y Neurociencias Prof. E. De Robertis ,PROBICENE-CONICET, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina;(2) Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina;(3) IQUIFIB-CONICET, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Iunín 956, 1113 Buenos Aires, Argentina |
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Abstract: | In the search of Na+,K+-ATPase modulators, we have reported the isolation by gel filtration and HPLC of a brain fraction, termed endobain E, which highly inhibits Na+,K+-ATPase activity. In the present study we compared some properties of endobain E with those of ascorbic acid. Kinetic experiments assaying synaptosomal membrane K+-p-nitrophenylphosphatase (K+-p-NPPase) activity in the presence of endobain E or ascorbic acid showed that in neither case did enzyme inhibition prove competitive in nature versus K+ or p-NPP concentration. At pH 5.0, endobain E and ascorbic acid maximal UV absorbance was 266 and 258 nm, respectively; alkalinization to pH 14.0 led to absorption drop and shift for endobain E but to absorbance disappearance for ascorbic acid. After cysteine treatment, endobain E absorbance decreased, whereas that of ascorbic acid remained unaltered; iodine treatment led to absorbance drop and shift for endobain E but to absorbance disappearance for ascorbic acid. HPLC analysis of endobain E disclosed the presence of two components: one eluting with retention time and UV spectrum indistinguishable from those of ascorbic acid and a second, as yet unidentified, both exerting Na+,K+-ATPase inhibition. |
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Keywords: | Endobain K+-p-nitrophenylphosphatase inhibitor Na+,K+-ATPase inhibitor ascorbic acid |
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