Cyclooxygenase-2 (COX-2) and the kidney: current status and potential perspectives.

Prostaglandins are important mediators of renal physiology and disease. The main enzyme which governs the synthesis of prostaglandins is cyclooxygenase (COX), also called prostaglandin endoperoxide synthase (PGS). Until recently it was assumed that only one cyclooxygenase gene and protein exists, an enzyme which is now called cyclooxygenase-l (COX-I) or the 'constitutive' isoform. Between 1989and 1991 however, several groups reported evidence for the existence of a mitogenand endotoxin-inducible cyclooxygenase, a second isoform of cyclooxygenase. This so-called 'inducible' enzyme was named cyclooxygenase-2 (COX-2) [1,2]. The terms 'constitutive' and 'inducible' are actually inadequate since COX-2 is also constitutively expressed in some organ systems including the kidney [3-5], and there is evidence that COX-l mRNA expression can be regulated under certain circumstances [1,2]. COX-2 products have been found to be important also in kidney development and cell differentiation [6,7].