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

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 (10µM) was added on the 5-HT (1.0µM) - induced sustained contractile response. Similarly, functional characterization of Na⁺ , K⁺ -ATPase activity was done by K⁺ -induced relaxation (10µM-10mM) in the absence and presence of ouabain (0.1µM/ 0.1mM), digoxin (0.1µM) and barium (30µM).
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 : 0.479mM) inhibited K⁺ -induced relaxation suggesting K_ir (inward rectifier) channel in part had role in K⁺ -induced vasodilatation in ruminal artery. Vasorelaxant effect of KCl (10µM-10mM) in K⁺ -free medium is also blocked by ouabain (0.1µM and 0.1mM) (IC₅₀ :0.398mM and IC₃₅ : 1.36mM), but not by digoxin (0.1µM) (IC₅₀ 0.234mM) 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.