title: Effect of acute iNOS inhibition on glomerular function in tubulointerstitial nephritis.
abstract: BACKGROUND
  Tubulointerstitial nephritis (TIN) is characterized by progressive inflammatory infiltrate of the renal interstitium, induction of cortical tubular inducible nitric oxide synthase (iNOS) and reductions in glomerular filtration rate (GFR). These studies were designed to examine the changes in glomerular hemodynamics 7 and 21 days after induction of TIN and to evaluate the effect of acute iNOS blockade on glomerular function in the early stages of this model.
  
  
  METHODS
  TIN was induced by immunizing Brown Norway rats with renal tubular antigen in complete Freund's adjuvant (RTA/CFA). Control rats were immunized with CFA alone. Micropuncture and morphologic studies were performed 7 and 21 days after immunization.
  
  
  RESULTS
  Histology revealed minimal peritubular and interstitial inflammation in the RTA/CFA group one week after immunization while extensive interstitial inflammation with few preserved superficial nephron was observed three weeks after RTA/CFA immunization. Micropuncture studies on day 7 in the RTA/CFA group revealed a significant reduction in single nephron GFR due to a profound reduction in nephron plasma flow and in the ultrafiltration coefficient. Studies performed on day 21 revealed that single nephron GFR (SNGFR), nephron plasma flow (SNPF) and the ultrafiltration coefficient had returned to the normal baseline value despite the severe reduction in GFR. To assess the role of increased nitric oxide production secondary to iNOS induction on the glomerular hemodynamic changes observed in the early stages of the disease, the iNOS blocker (l-N(6)-iminoethyl lysine, L-NIL) was administered IV (1 mg/h) in RTA/CFA rats and CFA rats. L-NIL had no effect in CFA rats but produced significant increases in GFR, SNGFR and SNPF in RTA/CFA rats.
  
  
  CONCLUSIONS
  These results demonstrate that TIN is associated with a progressive reduction in GFR, which is likely the result of functional vasoconstriction and decreases in the ultrafiltration coefficient in the early stages of the disease and on a significant reduction in the number of functioning nephron in the later stages. Induction of iNOS with increased NO production actively participates in the functional changes observed in the early stages of the disease most likely by inhibiting normal endothelial NOS activity.
authors.affiliation: Division of Nephrology-Hypertension 9111-H, University of California San Diego School of Medicine, La Jolla, CA, USA. fgabbai@vapop.ucsd.edu
authors.forename: Francis B
authors.initials: FB
authors.lastname: Gabbai
authors.forename: Terry C
authors.initials: TC
authors.lastname: Hammond
authors.forename: Scott C
authors.initials: SC
authors.lastname: Thomson
authors.forename: Ser
authors.initials: S
authors.lastname: Khang
authors.forename: Carolyn J
authors.initials: CJ
authors.lastname: Kelly
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology; D005620:Freund's Adjuvant / Q000276:immunology; D005919:Glomerular Filtration Rate; D006439:Hemodynamics / Q000187:drug effects; D007678:Kidney Glomerulus / Q000098:blood supply / Q000503:physiopathology*; D008239:Lysine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D009395:Nephritis, Interstitial / Q000276:immunology / Q000473:pathology / Q000503:physiopathology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D052247:Nitric Oxide Synthase Type II; D011677:Punctures; D051381:Rats; D011914:Rats, Inbred BN; D013997:Time Factors
chemical_list: D000941:Antigens; C090663:N(6)-(1-iminoethyl)lysine; C035812:renal tubular antigen; D005620:Freund's Adjuvant; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D008239:Lysine