Figure 2.

Preserved endothelium-independent relaxation and increase in intracellular Ca²⁺ levels upon stimulation by agonists, and a failure of antihypertensive therapy to improve the reduced EDHF-mediated responses in eNOS-KO mice. (a) Endothelium-independent relaxation in small mesenteric arteries to levcromakalim was preserved (left, n = 6 each) while those to SNP were enhanced (right, n = 5–6) in eNOS-KO mice. ^AP < 0.01. (b) Direct measurement of the changes in intracellular Ca²⁺ levels in endothelial cells. ACh (1 nM–10 μM), CPA (3 μM), and ionomycin (25 μM) caused an increase, while EGTA (2 mM) caused a decrease in intracellular Ca²⁺ levels as shown by F348/F380 (left). The increase in intracellular Ca²⁺ levels, when normalized to ionomycin-induced maximal F348/F380, were comparable between the two strains (right, n = 5 each). (c) Although the antihypertensive therapy with hydralazine for 6 weeks normalized blood pressure in eNOS-KO mice (left), the treatment failed to improve the reduced EDHF-mediated responses (KCl-sensitive component after the blockade of cyclooxygenase with 10 μM indomethacin and the blockade of eNOS with 100 μM L-NNA) in eNOS-KO mice (right, n = 8–10). ^AP < 0.01, ^BP < 0.05 vs. control. sBP, systolic blood pressure.