Effect of Ang II infusion and COX1 and COX2 deficiency on renal medullary PGE2 and PGI2 synthesis. Prostanoids were measured by gas chromatography/mass spectrscopy in snap-frozen papillae dissected from mice pretreated with the COX2 inhibitor (COX2 inh.), vehicle-treated mice, or COX knockout mice with or without acute infusion of Ang II for 30 minutes. *P < 0.01 and #P < 0.05 vs. control.