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KMID : 0390119930330010127
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Journal of Pusan Medical College
1993 Volume.33 No. 1 p.127 ~ p.138
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Characteristic of a Na+/H+ Exchanger in Rabbit Brain Synaptosome
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Abstract
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The properties of Na+/H+ exchanger in the synaptosomes have been studied primarily by using acridine orange absorbance ot follow H+ efflux.
Acridine orange absorbance was decreased by a preset pH gradient(intravesicular acid), and the inital rate of the dissipation of a preset pH gradient was accelerated by pule injection of sodium in a saturable manner.
The basal properties of Na+/HA+ exchanger in the synaptosome were similar to those ofund on renal cortical Na+/H+ exchanger. I)Na+ and only one binding site on the exchanger. II)Vmax was larger in renal brush border membrane vesicle(BBMV) than
the
synaptosome, but Kna of the synaptosome was similar to that of renal brush border membrane vesicle. iii) Li+ could be successfully substituted for Na+; its affinity for the exchanger was higher than that of Na+, but the maximal rate of H+ efflux
in
the
presence of Li+ was about 2 times lower than the maxmial rate of H+ efflux in the presence of Na. However, the Na+/H+ exchanger of the synaptosome exhibited greater sensitivity to inhibition by amiloride and cimetidine than the Na+/H+ exchanger
of
the
renal cortical brush border.
These results might indicate that the Na+/H+ exchanger is present in the synaptosome and the exchanger of the synaptosome is kinetically similar to that of renal brush border, but two systems are pharmacologically distinct.
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KEYWORD
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