title: Erythrocyte sodium-lithium countertransport and proliferative diabetic retinopathy.
abstract: OBJECTIVE
  To investigate whether elevated erythrocyte Na+/Li+ countertransport (Na+/Li+ CT) activity is present in patients with proliferative diabetic retinopathy (PDR).
  
  
  METHODS
  The rate of Na+/Li+ CT activity assayed in 21 patients with type 1 diabetes mellitus (DM) presenting PDR was compared with 10 patients with nonproliferative retinopathy (NPDR) and with 11 patients with normal fundi. Twelve normal volunteers with no family history of hypertension were used as a control group. The albumin excretion rate was determined by nephelometry, and the glomerular filtration rate was measured by the plasma clearance of eidetic acid labeled with chromium-51.
  
  
  RESULTS
  Patients with PDR showed higher diastolic blood pressure levels (mean +/- SD) compared with those with NPDR or normal fundi (95 +/- 13 versus 90 +/- 09 and 82 +/- 19 mm Hg, P = 0.02, respectively). The albumin excretion rate was higher [geometric mean (range)], and the glomerular filtration rate was lower (mean +/- SD) in patients with PDR than in those with NPDR or normal fundi [333 (2 to 5140) versus 32 (5.9 to 2200) and 6 (1.5 to 306) microg/min, P = 0.01, and 63 +/- 33 versus 99 +/- 37 and 93 +/- 43 ml/min, P = 0.02, respectively]. The mean Na+/Li+ CT in patients with PDR was significantly higher than in patients with NPDR or normal fundi and control group (0.46 +/-0.20 versus 0.32 +/- 0.12, 0.32 +/- 11, and 0.21 +/- 0.07 mM/L red blood cells (RBC)/h, respectively, P = 0.0001). In a multiple logistic regression analysis, with PDR as the dependent variable, Na+/Li+ CT (odds ratio [OR]: 4.7, confidence interval [CI]: 1.2-17.6, P = 0.02), diastolic blood pressure (OR, 3.4; CI, 1.3 to 9.6; P = 0.018), and glomerular filtration rate (OR, 5.1; CI, 1.6-17.7; P = 0.007) were the only variables that were maintained in the equation, indicating that they were the main determinants of PDR.
  
  
  CONCLUSIONS
  Patients with type 1 DM and proliferative retinopathy have elevated erythrocyte Na+/Li+ CT.
authors.affiliation: Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas (UNICAMP), SP, Brazil.
authors.forename: J M
authors.initials: JM
authors.lastname: Lopes de Faria
authors.forename: L A
authors.initials: LA
authors.lastname: Silveira
authors.forename: M
authors.initials: M
authors.lastname: Morgano
authors.forename: E J
authors.initials: EJ
authors.lastname: Pavin
authors.forename: J B
authors.initials: JB
authors.lastname: Lopes de Faria
mesh_terms: D000293:Adolescent; D000328:Adult; D017920:Antiporters / Q000378:metabolism*; D001794:Blood Pressure; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D003930:Diabetic Retinopathy / Q000097:blood*; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008094:Lithium / Q000097:blood*; D008297:Male; D008875:Middle Aged; D012964:Sodium / Q000097:blood*
chemical_list: D017920:Antiporters; C045885:sodium-lithium countertransporter; D008094:Lithium; D012964:Sodium