Renal identification of cyclooxygenase-2 in a subset of thick ascending limb cells.
The prostaglandin G2/H2 synthase (cyclooxygenase, COX) is a key regulatory enzyme of prostanoid synthesis pathway. The message-encoding COX isoenzymes (constitutive COX-1 and inducible COX-2) have been described in the rat kidney. However, there is scarce information on the localization of COX-2 in the kidney, although it has been recently reported to be localized in the macula densa. The present study was designed to evaluate the localization of COX-2 in adult rat kidneys. Normal rat kidneys (n=10) were fixed in Bouin and were immunostained with specific antibodies against COX-2 by the peroxidase method. The cellular origin of COX-2 was assessed by the immunostaining of serial consecutive sections with antibodies against Na-K-ATPase, Tamm-Horsfall glycoprotein, H-K-ATPase, kallikrein, and macrophages. COX-2 was consistently observed in a subset of tubular cells located in the cortex and in the outer medulla. The staining of serial sections showed that the COX-2+ cells contained both Na-K-ATPase and Tamm-Horsfall, indicating that they corresponded to thick ascending limb (TAL) cells. They were observed at a considerable distance from the corresponding macula densa, although occasionally they were observed close to glomeruli. The COX-2 staining in the TAL cells was not abolished by dexamethasone treatment (1 to 20 mg/kg), suggesting its constitutive expression in normal kidneys. The presence of COX-2 in TAL (a tubular segment postulated to be devoid of COX-1) may contribute to the handling of ions through local production of prostaglandins.
Vio
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CP
Departamento de Ciencias Fisiologicas, Facultad de Ciencias Biologicas, Pontificia Universidad Catolica de Chile, Santiago. cvio@genes.bio.puc.cl
Cespedes
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Gallardo
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Masferrer
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D000818:Animals; D051546:Cyclooxygenase 2; D007527:Isoenzymes / Q000032:analysis*; D007668:Kidney / Q000166:cytology / Q000201:enzymology*; D008297:Male; D011451:Prostaglandin-Endoperoxide Synthases / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D007527:Isoenzymes; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D000254:Sodium-Potassium-Exchanging ATPase