S. Abdalla et Ja. Will, POTENTIATION OF THE HYPOXIC CONTRACTION OF GUINEA-PIG ISOLATED PULMONARY-ARTERIES BY 2 INHIBITORS OF SUPEROXIDE-DISMUTASE, General pharmacology, 26(4), 1995, pp. 785-792
1. Isolated proximal and distal extralobar branches of the pulmonary a
rtery of the guinea-pig develop slow and well-sustained contractions i
n response to hypoxia (P-O2 11-15 mm Hg) without prior stimulation wit
h an agonist. These contractions are readily reversible by readministr
ation of oxygen. 2. Incubation of these preparations with diethyldithi
ocarbamic acid (DETCA, 5 mM for 30 min), an inhibitor of superoxide di
smutase, significantly increased the hypoxic contractions whether DETC
A was added before the challenge with hypoxia or after the hypoxic con
traction had reached a plateau. This treatment also reduced the oxygen
-induced relaxation. 3. Similarly, incubation with triethylenetetramin
e (TETA, 5 mM for 30 min), another inhibitor of superoxide dismutase,
produced larger potentiation of the hypoxic contraction in the two pre
parations and reduced the oxygen-induced relaxation. 4. Furthermore, a
ddition of H2O2 (10(-5) M-3 x 10(-4) M) caused concentration-dependent
relaxation of the hypoxic contraction while larger concentrations (10
(-3) M and 3 x 10(-3) M) caused contraction that did not respond to re
administration of oxygen. 5. These observations suggest that during hy
poxic stress, the accumulation of superoxide anions may participate in
the hypoxia-induced contraction and that the metabolism of these radi
cals into H2O2 by superoxide dismutase maintains the relaxed state dur
ing normoxia.