Selective increase of cyclooxygenase-2 expression in a model of renal ablation.
Previous studies have suggested a possible role for prostaglandins (PGs) in mediating alterations in nephron structure and function ensuing after renal ablation. Two isoforms of cyclooxygenase (COX) have been described: constitutive (COX-1) and inducible (COX-2). We examined expression of these isoforms following subtotal renal ablation (5/6 ablation, RA) in rats. In renal cortex, COX-2 mRNA and immunoreactive protein (IP) increased progressively compared with sham-operated littermates. In contrast, there were no significant changes in COX-1 mRNA expression. In normal kidney, cortical COX-1 IP was immunolocalized predominantly to mesangial cells and collecting tubules, whereas COX-2 IP was found in a subset of cortical thick ascending limb of Henle's loop (CTAL) cells in the region of the macula densa (MD). Following RA, significantly increased COX-2 IP was detected in the MD and surrounding CTAL cells. In addition, fainter immunoreactive COX-2 was detected in scattered visceral epithelial cells and mesangial cells of the glomerulus. Immunoblotting of isolated glomeruli demonstrated a selective increase of glomerular immunoreactive COX-2 expression following RA. No change of COX-1 expression was seen. To determine COX activity, isolated glomeruli were incubated with arachidonic acid and PGE2 measured by enzyme immunoassay (EIA). Compared with sham, glomeruli from 2 wk RA produced significantly more PGs. SC-58560, a selective COX-1 inhibitor, did not inhibit PG production in the remnant glomeruli at concentrations up to 10(-4) M, whereas SC-58236, a relatively selective COX-2 inhibitor, significantly inhibited PG production by RA glomeruli. In preliminary studies, to define mechanisms of altered expression of glomerular COX-2, rat mesangial cells were incubated with serum from sham or 2 wk RA. There were significant increases in COX-2 expression in response to 2 wk RA serum. In summary, these results indicate selective increases in renal cortical COX-2 expression following renal ablation.
George M. O'Brien Kidney and Urologic Diseases Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
J L
JL
Wang
H F
HF
Cheng
M Z
MZ
Zhang
J A
JA
McKanna
R C
RC
Harris
D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure; D002478:Cells, Cultured; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000378:metabolism; D004790:Enzyme Induction; D005920:Glomerular Mesangium / Q000166:cytology / Q000201:enzymology*; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics; D007668:Kidney / Q000502:physiology*; D007672:Kidney Cortex / Q000201:enzymology*; D007678:Kidney Glomerulus / Q000166:cytology / Q000201:enzymology*; D008297:Male; D008565:Membrane Proteins; D009392:Nephrectomy; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014158:Transcription, Genetic
D007527:Isoenzymes; D008565:Membrane Proteins; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C496513:Ptgs1 protein, rat; D015232:Dinoprostone