Fig. 8.

Vasodilatory dose-response curves of nitrite on vascular rings from rat aorta and a branch of the sheep femoral artery. A: endothelium-intact rings were preconstricted with 5-hydroxy-tryptamine (5-HT; 10 μM) in the presence of 100 μM l-NAME and then exposed to stepwise increases of nitrite in the bath solution (Krebs-Henseleit, pO₂ 6.2 ± 1.0 Torr). EC₅₀ values are −4.0 ± 0.3 (sheep) and −5.2 ± 0.1 (rat), indicating ∼15-fold (P < 0.01) greater sensitivity of rat arteries to nitrite. B: in contrast, there are no significant differences between the dose response curves of sheep and rat arteries exposed to NO from the donor PROLI-NO. Relaxation is expressed as percent change from plateau tension after 5-HT-induced contraction. Data are corrected for spontaneous relaxation of rings from the same animal exposed to saline instead of nitrite. Results are for 5 animals for each group and are based on means of 3 nitrite, 3 NO, and 3 control vessel rings from each animal. Means are ± SE.