title: Tubular and interstitial cell apoptosis in the streptozotocin-diabetic rat kidney.
abstract: OBJECTIVE
  Angiotensin II (Ang II) mediates progressive nephron loss in diabetes and stimulates apoptotic cell death in several tissues. We studied the extent of apoptosis in streptozotocin (STZ) induced diabetic nephropathy in the rat and the effects of insulin and type 1 (AT1) or type 2 (AT2) Ang II receptor blockade with losartan or PD123319, respectively.
  
  
  METHODS
  Three groups of rats were studied after 2 and 12 weeks: (1) controls; (2) STZ-diabetic rats (STZ rats), and (3) STZ-diabetic rats with insulin implants. Additional rats were treated with losartan (25 mg/kg/day) and/or PD123319 (10 mg/kg/day) for 2 weeks. Kidneys were examined for apoptosis, using the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, DNA laddering, and electron microscopy. Immunoblotting determined expression of the proapoptotic protein Bax and of the antiapoptotic protein Bcl-2 in proximal tubules.
  
  
  RESULTS
  Diabetes caused a significant increase in apoptosis, involving tubular and interstitial cells of cortex and medulla, but not glomerular cells (2 weeks: controls 264 +/- 94 vs. STZ rats 1,501 +/- 471 apoptotic nuclei/kidney section; p < 0.02; n = 6-8), an effect reversed by insulin. In STZ rats, ultrastructural examination revealed chromatin condensation and nuclear fragmentation in tubular and interstitial cells. At 2 and 12 weeks, a significant decrease in the expression of the antiapoptotic protein Bcl-2 occurred in STZ rat proximal tubules, with restoration by insulin. In STZ rats, treatment for 2 weeks with losartan or PD123319 inhibited apoptosis in the kidneys, with no additive effect of the combination therapy.
  
  
  CONCLUSIONS
  Apoptosis occurs in diabetic nephropathy, involving tubular and interstitial cells, an effect reversed by insulin therapy. Furthermore, the effects of AT1 or AT2 receptor blockade suggest that Ang II is involved in mediating apoptosis in the diabetic kidney.
authors.affiliation: Division of Nephrology, Department of Medicine, The Ottawa Hospital, Ottawa, Ont., Canada.
authors.forename: Dinender
authors.initials: D
authors.lastname: Kumar
authors.forename: Joseph
authors.initials: J
authors.lastname: Zimpelmann
authors.forename: Susan
authors.initials: S
authors.lastname: Robertson
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Burns
mesh_terms: D057911:Angiotensin Receptor Antagonists; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000473:pathology*; D003928:Diabetic Nephropathies / Q000378:metabolism / Q000473:pathology*; D007093:Imidazoles / Q000494:pharmacology; D007668:Kidney / Q000473:pathology* / Q000648:ultrastructure; D007684:Kidney Tubules / Q000473:pathology* / Q000648:ultrastructure; D019808:Losartan / Q000494:pharmacology; D008297:Male; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D051028:bcl-2-Associated X Protein
chemical_list: D057911:Angiotensin Receptor Antagonists; C494828:Bax protein, rat; D007093:Imidazoles; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011725:Pyridines; D051028:bcl-2-Associated X Protein; C073402:PD 123319; D019808:Losartan