The effects of cyanide and its interactions with norepinephrine on isolated aorta strips from the rabbit, dog, and ferret.

Effects of sodium cyanide on isolated strips of rabbit, dog, and ferret aorta were determined. In the rabbit aorta strip, cumulatively added cyanide caused small contractions beginning at approximately 10(-11) M cyanide and reaching a maximum response at 10(-5) M. A concentration of cyanide between 10(-5) M and 10(-3) M produced relaxation. When cyanide was cumulatively added to norepinephrine (NE)-contracted rabbit aorta strips, no contractions were observed. Cyanide concentrations above 10(-5) M produced relaxation in the NE-contracted vessels. Sensitivity of the aorta strips to NE differed among the species examined. The ED50 for contractions in the dog and ferret aorta was 4 X 10(-4) M and in the rabbit was 5 X 10(-6) M. Pretreatment with cyanide in concentrations up to 10(-2) M did not reduce contractions of dog aorta to NE, although 10(-2) M cyanide abolished contractions of rabbit aorta to NE and reversed NE-contractions of ferret aorta to relaxation. The antagonism of cyanide for NE-induced contractions was completely reversible with cyanide concentrations up to 10(-3) M. Cyanide pretreatment of strips of aorta increased the rate of contraction to NE. A concentration of 10(-2) M cyanide caused small contractions of aorta strips from each species. Thus, cyanide exerts dose and species dependent responses on vascular smooth muscle.