| Abstract: | In experiments on isolated porcine and canine coronary artery rings it was shown that vascular smooth muscle (VSM) during hypoxia (decreasing bath PO2 with 147 to 20-15 mm Hg) response to biphasic constriction-dilation reaction. Transient hypoxic contractions (THC) of VSM preserved completely in Ca2+-free solution and partially (up 50-60%) in the presence of Ca2+-channel blockers, but abolished by procaine. THC of VSM skinned by saponin significantly depressed at depletion of Ca2+-store sarcoplasmic reticulum (SR) by caffeine nd abolished after SR destruction. THC is not linked with Na+-K+-ATPase inhibition because it preserved (or increased) at ouabain treatment. THC significantly depressed under selective glycolysis blockade by monoiodoacetic acid and pyruvate and also after inositol-1 monophosphatase inhibition by lithium (the phase of hypoxic relaxation of VSM was augmented in this condition). Our results indicate that transient contraction of coronary arteries under hypoxia may be mediated mainly by release of Ca2+ from SR and linked obviously with production of inositol-1,4,5-trisphosphate. The participation of glycolysis in this process is unknown. |
