INFLUENCE OF 4-AMINO-5-(2-AMINOPHENYL)-2,4-DIHYDRO-3H-1,2,4-TRIAZOLO-3-THIONE ON Na + /Ca 2+ - EXCHANGER OF SMOOTH MUSCLE CELLS OF THE RAT AORTA
The aim of this investigataton has feen defervination in flence of the Na + /Ca 2+ exchanger in vasorelaxation induced by 4-amino-
5-(2-aminophenyl)-2,4-dihydro-3n-1,2,4-triazolo-3-thione (D-378) , in rat aortic rings. It was found that D-378 has a relaxant
activity and in dependence of concentration, inhibits aortic ring contraction induced by low Na + solution and ouabain.
Comparison of obtaived results showed that D-378 suppressed aortic ring contraction induced by these two procedures in almost
the same extent and with approximately similar IC 50 values. Because the contractions induced by the low Na + solution and
ouabain were mainly due increasing Ca 2+ influx mediated by the reverse mode of the Na + /Ca 2+ exchanger, these data indicate that
the inhibitory effect of D-378 results from a direct blockade of Ca 2+ influx through exchanger. Taken together, these results
provide some evidence that D-378 strongly inhibits Ca 2+ influx through the Na + /Ca 2+ exchanger, suggesting that this effect of
triazole may also be related to it`s vasodilating activity. The fact that D-378 has a significant ability to block the influx of Ca 2+
through the Na + /Ca 2+ exchanger may be important in some pathological conditions when the exchanger operating in reverse mode
has caused Ca 2+ overload and therefore may increase overall vasoconstriction..
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