The similarity in action of hypoxia and platelet-activating factor on smooth muscle cells of coronary arteries: possible explanation for hypoxic coronary spasm development.

Studies in isolated smooth muscles and single cells of coronary arteries have demonstrated that both hypoxia and platelet activating factor (PAF) in a similar manner increased contractile force and Ca-activated K currents. The specific antagonists of PAF receptors BN 52021 and WEB 2886 significantly decreased contractile responses of vascular smooth muscle (VSM) to PAF and hypoxia. Taken together, these data allow to suggest that endogenous PAF can produce both phasic and tonic contraction in coronary arteries under hypoxic condition.