Effects of diuretics on the vasoconstrictor responses to norepinephrine and potassium ions in the rat mesenteric artery.

The effects of four different diuretics, hydroflumethiazide, furosemide, piretanide and potassium canrenoate on the vascular responses to norepinephrine and potassium chloride in the perfused rat mesenteric vascular bed have been studied. Furosemide or piretanide in the perfusate inhibited the vascular response to norepinephrine in a dose-related manner, while the vascular contraction induced by potassium chloride was not affected by these substances. In contrast to furosemide and piretanide, potassium canrenoate inhibited vascular responses to both norepinephrine and potassium ions. Hydroflumethiazide did not induce any change in the vascular response to norepinephrine or to potassium chloride. From these results, it is suggested that furosemide, piretanide and potassium canrenoate, but not hydroflumethiazide have direct vascular actions independent from their renal actions which may contribute to their antihypertensive effects.