A comparison of the effects of hydrallazine, diazoxide, sodium nitrite and sodium nitroprusside on human isolated arteries and veins.

1 Human common palmar digital arteries and dorsal metacarpal veins have been studied in vitro to investigate the responses of arterial and venous muscle to hydrallazine, diazoxide, nitroprusside and sodium nitrite. 2 Tissues were removed at autopsy, cut into helical strips and suspended in organ baths under identical conditions. The contractile response to noradrenaline was tested in the presence of the same concentrations of the vasodilator drugs in arteries and veins. 3 Hydrallazine antagonised contraction of arteries, but not veins to noradrenaline. Diazoxide, nitroprusside or sodium nitrite antagonised responses in both arteries and veins. Diazoxide and nitrite were more effective on arteries and nitroprusside was more effective on veins. 4 These results are in accord with clinical observations and confirm that there are differences in the susceptibility of human arterial and venous smooth muscle to vasorelaxant drugs.