Postnatal development of cyclooxygenase-2 in the rat kidney

Prostaglandins an local mediators/modulators of kinin effects in the kidney . The prostaglandin G2/H2. synthase (cyclooxygenase, COX) is the key regula tory enzyme of prostanoid synthesis pathway. Two COX isoenzymes (constituti ve or COX-1 and inducible or COX-2) have been described in the rat kidney. We have demonstrated the presence of COX-2 in a subset of thick ascending l imb of Henle (TAL) cells in normal adult rats [Vio, C.P., Cespedes, C., Gal lardo, P., Masferrer, J.L., 1997. Renal identification of cyclooxygenase-2 in a subset of thick ascending limb cells. Hypertension 30, 687-692]. The p resent work was designed to evaluate COX-2 during the postnatal development of the rat kidney. Kidneys from Sprague-Dawley rats were studied during po stnatal days 5, 10, 15 days and adult (60 days) (n = 8 each group). Renal t issue was immunostained with specific antibodies against COX-2. COX-2 was o bserved exclusively in TAL. A small number of COX-2 cells were observed dur ing early postnatal life, increasing from day 5 to 15, and decreasing there after to reach adult levels. During maximal expression, near 20% of TAL wer e COX-2 positive whereas in early postnatal period and adults, only 2% of T AL cells contain COX-2. This transient induction of COX-2 during developmen t suggest that the enzyme is necessary for the postnatal development of the kidney. This change in COX-2 seems to correspond to a derepression of COX- 2 gene expression secondary to low levels of glucocorticoids. (C) 1999 Else vier Science B.V. All rights reserved.