Vasorelaxation of goat mesenteric artery is mediated by endothelial Na+‑K+‑ATPase

Objective: To examine the role of Na+‑K+‑ATPase and K+ channels in mediating vasorelaxation in the superior mesenteric artery of Capra hircus. Materials and Methods: Goat superior mesenteric artery (GSMA) was cut into 1.5–2 mm circular rings and mounted in a thermostatically controlled (37°C ± 0.5°C) organ bath containing 20 ml of modified Krebs‑Henseleit saline (MKHS) (pH 7.4), with continuous aeration under 1.5 g tension for 90 min. Endothelium‑intact (ED+) or endothelium‑denuded (ED−) GSMA ring was contracted with phenylephrine (PE) or 5‑hydroxytryptamine (5‑HT) (1 μM–0.1 mM) in the absence or presence of ouabain (0.1 µM). KCl (1 μM–10 mM) was added cumulatively to K+‑free MKHS‑pre‑contracted (ED+/−) rings in the absence or presence of ouabain (0.1 μM) or barium (1 μM) or 4‑aminopyridine (1 μM). Results: Ouabain did not alter the basal tone of the arterial ring. The contractile response induced by PE (Emax: 50.46 ± 2.68, pD2: 5.53 ± 0.04) and 5‑HT (Emax: 30.86 ± 1.33, pD2: 6.17 ± 0.03) in ED+ ring was significantly (P < 0.001) augmented in ED− rings (PE: Emax: 93.30 ± 2.11, pD2: 6.41 ± 0.04; 5‑HT: Emax: 95.07 ± 0.99, pD2: 6.27 ± 0.03). The contractile response induced by PE and 5‑HT in ED+ or ED− rings in the presence of ouabain was almost identical with that of ED− rings. Vasorelaxation of KCl (Emax: 2.90 ± 1.14, pD2: 3.9 ± 0.03) was significantly attenuated in the presence of ouabain (Emax: 73.8 ± 5.16, pD2: 4.3 ± 0.04), Ba2+ (Emax: 16.34 ± 4.7, pD2: 3.22 ± 0.02), 4‑AP (Emax: 18.16 ± 2.4, pD2: 3.68 ± 0.03), ouabain and Ba2+ (Emax: 70.09 ± 3.66, pD2: 4.41 ± 0.04), and ouabain and 4‑AP (Emax: 66.98 ± 4.61, pD2: 4.13 ± 0.06). Conclusion: The vasorelaxation in GSMA is mediated by the endothelium‑derived hyperpolarizing factor (EDHFs) such as ouabain‑sensitive Na+‑K+‑ATPase, KIR and Kv channels.