Furosemide antagonizes the contractile response to noradrenaline on isolated rat tail artery

To determine the effect of furosemide (FUR) on the noradrenaline (NA) contraction of arteries, experiments were performed on isolated rat tail arteries according to Nicholas. FUR (300 mumol/l, 3 mmol/l) as well as Ca2+ transport system inhibitor, verapamil (VER), decreased the NA contractile force and FUR (3 mmol/l) antagonized the effect of VER (10 and 100 nmol/l). Calculated dose ratios according to Stephenson indicated that FUR and VER compete not only with NA but with each other. FUR decreased Ca2+ concentration in rat arteries studied in vivo by atomic absorption spectrophotometric method as well. It could be assumed that FUR depresses the sensitivity to NA and antagonizes NA induced contraction of arteries acting on transmembrane Ca2+ transport system.