Role of Na ⁺ -K ⁺ ATPase enzyme in vascular response of goat ruminal artery

Abstract

Objective:To study the role of Na+, K+- ATPase enzyme in the vascular response of goat ruminal artery.Materials and Methods:Ruminal artery was obtained in chilled aerated modified Krebs-Henseleit solution (KHS) from a local slaughterhouse and transported in ice for further processing. The endothelium intact arterial ring was mounted in a thermostatically controlled (37 ± 0.5°C) organ bath containing 20 ml of modified KHS (pH 7.4) bubbled with oxygen (95%) and CO2 (5%) under 2g tension. An equilibration of 90 min was allowed before addition of drugs into the bath. The responses were recorded isometrically in an automatic organ bath connected to PowerLab data acquisition system. In order to examine intact functional endothelium, ACh (10 μM) was added on the 5-HT (1.0 μM) - induced sustained contractile response. Similarly, functional characterization of Na+, K+-ATPase activity was done by K+-induced relaxation (10 μM-10 mM) in the absence and presence of ouabain (0.1 μM/ 0.1 mM), digoxin (0.1 μM) and barium (30 μM).Results:ACh (10−5 M) did not produce any relaxing effect on 5-HT-induced sustained contractile response suggesting that vascular endothelium has no significant influence on the activation of sodium pump by extracellular K+ in ruminal artery. Low concentration of Ba2+ (30 μM) (IC50: 0.479 mM) inhibited K+-induced relaxation suggesting Kir (inward rectifier) channel in part had role in K+-induced vasodilatation in ruminal artery. Vasorelaxant effect of KCl (10 μM-10 mM) in K+-free medium is also blocked by ouabain (0.1 μM and 0.1 mM) (IC50:0.398 mM and IC35: 1.36 mM), but not by digoxin (0.1 μM) (IC50 0.234 mM) suggesting that ouabain sensitive Na+, K+-ATPase isoform is present in the ruminal artery.Conclusion:In the goat ruminal artery functional regulation of sodium pump is partly mediated by K+ channel and ouabain sensitive Na+, K+ ATPase.

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

“…[ 3 4 ] The role of the endothelium in sodium pump induced vasorelaxation varies between vascular beds and species. The vasorelaxation induced by vascular sodium pump has been reported to be endothelium dependent in human placental vessels,[ 5 ] mice femoral artery,[ 6 ] and rat aorta[ 7 ] and endothelium independent in goat ruminal artery[ 8 ] and rabbit aorta. [ 9 ] In small arteries like mesenteric bed, where the ratio of endothelium/smooth muscle increases, the endothelium plays a more important role in modulation of the expression of Na + -K + -ATPase.…”