Аннотация:Background
Soluble guanylate cyclase (sGC) is a crucial enzyme at
NO/cGMP-mediated vasodilation. There are NO-independent
mechanisms of sGC activation besides wellknown
enzyme activation by NO. Since 1966 oxatriazolium-
5-olate derivatives are known as hypotensive agents
at narcotized animals [1]. But the mechanism of their
activity is not clarified. The goal of this research is to
examine the ability of 3-(3-[1,2,4]triazolo)-oxatriazolium-
5-olate (AS-6) to generate NO, to activate sGC, and
to cause vasodilatation.
Material and Methods
The ability of AS-6 to generate NO was estimated by its
reaction with oxyhemoglobin in the presence and absence
of glutathione. Also NO (nitrite) formation in the presence
of AS-6 was measured by the Griess reaction. Activity
of sGC was measured by using purified enzyme from porcine
lung in the presence of 100 microM AS-6. cGMP formation
was measured by immunoenzymatic method. To
examine vasodilator activity of AS-6, perfusion pressure
responses of isolated tail artery (of male Wistar rats) precontracted
with 0.5 mikroM norepinephrine was measured.
AS-6 was perfused at concentrations 1·10-9–1·10-5
M.
Results
We demonstrated that AS-6 doesn't generate detectable
levels of NO both in the presence and absence of glutathione.
AS-6 at concentration 100 microM caused 29 ± 3-
fold activation of purified sGC in thiol-independent manner.
This activation was 2.0 ± 0.2-fold potentiated by 50
microM allosteric sGC activator YC-1 and completely
blocked by heme-dependent sGC inhibitor ODQ. In isolated
tail artery AS-6 caused concentration-dependent
(1·10-9–1·10-5 M) decrease of perfusion pressure with 26
± 6 % maximal decrease at 1·10-5 M.
Conclusion
AS-6 causes dose-dependent vasodilatation of isolated
systemic artery. It seems to be that AS-6 activates sGC in
heme-dependent NO-independent manner.