Role of endothelial factors in the specific response of mouse tumour-feeding arterioles to stimulation of 5-HT1 receptors

Abstract

Purpose : To investigate the possible role of endothelial mediators on the increased vasoconstriction to 5-HT1 receptor stimulation by the host-modified arterioles feeding a Meth-A tumour implanted in the flank of female Balb/c mice. Materials and methods : Using intravital microscopy, the response to the topical administration of the general 5-HT agonist 5-carboxamidotryptamine maleate (5-CT; 10-6 m to 10-4 m) by the tumour-feeding arterioles with the responses of tumourindependent arterioles and those of control arterioles from mice without tumour after antagonization or inhibition of the synthesis of endothelial mediators was compared. Results : The dramatically higher vasoconstriction to 5-CT observed in tumour-feeding arterioles than in tumourindependent or control arterioles still persisted when either nitric oxide synthase, cyclooxygenase, lipoxygenase, or phospholipase A2 were inhibited or when thromboxane A2 or endothelin were antagonized. Conclusions : It was concluded that the higher reactivity to 5-HT1 stimulation by tumour-feeding arterioles is not due to changes in endothelial mediator release but probably due to changes affecting arteriolar smooth muscle.