['Prostanoids produce significant effects on ureteral function and are synthesized by cyclooxygenase (COX) enzymes. COX is found in the 2 isoforms COX-1 (a constitutive form) and COX-2 (an inducible form). Due to the side effects associated with COX-1 inhibition there is great interest in selective COX-2 inhibition. We determined if COX-2 messenger (m)RNA and protein expression are regulated during ureteral obstruction.', 'mRNA analysis was performed using excess ureteral segments from 6 patients undergoing reconstructive procedures for chronic ureteral obstruction and 8 (normal ureter) undergoing donor nephrectomy after providing informed consent. All ureteral segments were snap frozen in liquid nitrogen and stored at -70C. RNA was isolated from the segments using phenol extraction and complementary DNA was synthesized by reverse transcription with murine leukemia virus reverse transcriptase (Promega Corp., Madison, Wisconsin). Semiquantitative reverse transcriptase-polymerase chain reaction was performed using specific COX-2 gene primers with ribosomal S26 primers serving as the housekeeping gene. The polymerase chain reaction product was quantified by agarose gel electrophoresis and phospho-imaging. The ratio of COX-2-to-S26 mRNA was compared. Additional segments were homogenized and total protein was extracted, separated via sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transferred to nitrocellulose membranes. These membranes were Western blotted for COX-2 and glyceraldehyde-3-phosphate dehydrogenase (housekeeping protein) with specific primary and secondary antibodies.', "The mean ratio of COX-2-to-S26 mRNA plus or minus standard error at 20, 22 and 24 cycles of amplification was 0.22 +/- 0.04 in the 8 normal ureters compared with 1.01 +/- 0.21 in the 6 obstructed ureters (unpaired Student's t test p = 0.004). Similarly the mean ratio of COX-2-to-glyceraldehyde-3-phosphate dehydrogenase protein on immunoblotting was 0.15 +/- 0.02 in the 8 normal ureters compared with 0.59 +/- 0.10 in the 6 obstructed ureters (p = 0.003)."] Is cyclooxygenase-2 expression up-regulated in obstructed human ureter?