(a and b) Effect of isozyme-selective COX inhibition on urinary volume (UV) (a) and sodium excretion (UNaV) (b). Urinary volume and sodium excretion were significantly reduced in mice receiving acute infusion of the COX2 inhibitor SC58236 (squares, n = 7) over 30 minutes, but not the COX1 inhibitor SC58560 (triangles, n = 5). *P < 0.05 vs. base-line; ^#P < 0.05 vs. the COX1 inhibitor. (c) The change in UV following acute Ang II infusion and sequential addition of Ang II plus a COX2 inhibitor in mice orally pretreated with the COX1 inhibitor (triangles, n = 12), COX2 inhibitor (squares, n = 8), and vehicle-treated controls (circles, n = 6). *P < 0.05 vs. base-line; ^#P < 0.05 vs. control or COX1 inhibitor–pretreated mice; ^†P < 0.05 in controls and mice pretreated with COX1 inhibitor vs. UV stimulated by Ang II only.