Fj. Dowell et W. Martin, THE EFFECTS OF PEROXYNITRITE ON RAT AORTA - INTERACTION WITH GLUCOSE AND RELATED SUBSTANCES, European journal of pharmacology, 338(1), 1997, pp. 43-53
Peroxynitrite (1-100 mu M) induced a concentration-dependent relaxatio
n of rat aortic rings; the log EC50 and maximum relaxation on endothel
ium-denuded rings were -5.31+/-0.03 and 105+/-5%, n = 6, respectively.
The presence of the endothelium significantly impaired this relaxatio
n (log EC50, -4.41+/-0.04; maximum relaxation, 71+/-4%; n = 6); an eff
ect which was reversed by the inhibitor of nitric oxide synthase, N-G-
nitro-L-arginine methyl ester (L-NAME; 100 mu M). Incubation with a hi
gh concentration of peroxynitrite (1 mM, 10 min followed by washout) h
ad no effect on subsequent relaxation to acetylcholine (0.01-1 mu M) I
t did, however, significantly depress subsequent contraction to phenyl
ephrine (1-300 nM). This depression was dependent upon the presence of
D-glucose in the Krebs solution, could be reversed by the inhibitor o
f soluble guanylate cyclase, methylene blue (10 mu M) and reversed spo
ntaneously after 2 h. When peroxynitrite (1 mM) was mixed with D-gluco
se (11 mM) and subsequently neutralised to remove unreacted peroxynitr
ite, a new more potent relaxant was formed. Despite this, the ability
of peroxynitrite (1-100 mu M) to produce relaxation of endothelium-den
uded rings was similar in normal and glucose-free Krebs. Glycerol (22
mM), which like D-glucose is membrane permeant, also reacted with pero
xynitrite (1 mM) to form a new more potent relaxant. L-cysteine (1 mM)
had no effect by itself on the tone of aortic rings and when present
in the tissue bath had no effect on the ability of peroxynitrite or ne
utralised peroxynitrite (1-100 mu M) to produce relaxation. It did, ho
wever, potentiate the relaxant actions of the products formed from the
reaction of peroxynitrite with D-glucose or glycerol. The membrane im
permeant sugars, mannitol and sorbitol (each 11 mM) also reacted with
peroxynitrite (1 mM), but expression of the vasorelaxant properties of
their respective derivatives was seen only in the presence of L-cyste
ine (1 mM). Membrane permeance cannot, however, explain why peroxynitr
ite reacts with D-glucose and glycerol, but not mannitol or sorbitol t
o form products with intrinsic relaxant activity, as the product forme
d from the impermeant sugar, L-glucose (11 mM), also has intrinsic act
ivity. The relaxant potency of this product was equipotent to that for
med from D-glucose and was also potentiated by L-cysteine (1 mM). Thes
e result confirm that peroxynitrite can react with glucose and other c
ompounds with alcohol functional groups to form vasorelaxant species.
The relaxation induced when peroxynitrite is added to rat aortic rings
is not, however, dependent upon this reaction since it occurs in gluc
ose-free Krebs. (C) 1997 Elsevier Science B.V.