RÉSUMÉ
Roles of sympathicus, sensory neuropeptides (SNP), metabolites of cyclooxygenase, metabolites of lipoxygenase, endothelium derived relaxing factor (EDRF), reactive oxygen (ROS) and potassium channels (PC) in the hypoxic pulmonary vasoconstriction (HPV) and hypoxic cerebral vasodilation (HCVD) were studied in intact rats, rabbits and dogs. Results were as follows: during hypoxia, the excitation of sympathicus results in a constriction of both pulmonary and cerebral vessels; SNP, EDRF and the opening of 4-AP sensitive PC caused the dilation of both of them; metabolites of lipoxygenase mediated HPV and HCVD, whereas metabolites of cyclooxygenase were their modulators; hypoxia induced blockade of the ATP sensitive PC mediated HPV, but had no effect on HCVD; reduction of O_2~+ in the lung might potentiate HPV, but had no effect on HCVD. It is suggested that the alteration of lipoxygenase metabolites, ROS and ATP sensitive PC are factors accounting for the difference in response of pulmonary and cerebral vassels to hypoxia.