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[Mechanisms of endothelium-dependent transient contraction of coronary artery smooth muscles during hypo-oxygenation].

The effect of endothelium on hypo-oxygenation--induced reactions of preactivated smooth muscle (SM) of the canine and porcine large coronary arteries, was studied. Decreased oxygenation of Krebs--bicarbonate solution (PO2-26.6-19.9 gPa) resulted in biphasic changes in the preparation with intact endothelium: a considerable relaxation was preceded by transient contractions. After removal of the endothelium a transient increase of tension was reduced or absent. Blockade of prostaglandins, leukotrienes and free radicals did not affect hypo-oxygenation-induced contraction of the VSM. The data suggest that endothelium can modulate the response of the coronary arteries SM to decrease in oxygen tension. Endothelium-dependent transient contraction during hypo-oxygenation is mediated through the increase of cGMP production.