Effect of frusemide on the reactivity of rat portal vein

Short lengths of rat portal vein were suspended in Krebs bicarbonate solution. Contractile responses to noradrenaline and angiotensin II and the parameters of spontaneous contractions were determined before and after addition of frusemide at 10–⁶ and 10–⁴ g/ml. Frusemide at 10–⁶ g/ml slightly suppressed the amplitude of spontaneous contractions and slightly decreased the responses to noradrenaline and angiotensin II. At 10–⁴ g/ml the drug had a much greater inhibitory effect on endogenous and exogenous stimulation. The concentrations used appear to be similar to those achieved during effective diuretic and hypotensive treatment. It is postulated that frusemide may have a direct inhibitory action on the reactivity of vascular smooth muscle mrticularlv in the capacitance vessels.