Tyrosine kinase pathway has been shown to be involved in the effects of hypoxia in pulmonary arteries, but its role in pulmonary vein is not known. The aims of this study were to determine the effect of hypoxia in sheep isolated pulmonary veins and to identify the role of tyrosine kinase pathway in hypoxic response. Genistein and tyrphostin were used as selective tyrosine kinase inhibitors, and sodium orthovanadate was administered for tyrosine kinase activation. Hypoxia (95% N-2 to 5% CO2) caused a vasoconstriction either under resting tone or in U46619-precontracted pulmonary veins. Genistein and tyrphostin inhibited hypoxia-induced vasoconstriction both under resting tone and in precontracted veins, while sodium orthovanadate increased these hypoxic contractions. Our findings suggest that tyrosine kinase pathway is involved in hypoxic pulmonary vasoconstriction in sheep isolated pulmonary vein rings. (C) 2003 Elsevier Inc. All rights reserved.