Measurement of Effective Renal Plasma Flow with 99mTc- MAG-3 in Type 2 Diabetes

  • Elif Ekinci, Austin Health, Heidelberg, Victoria, Australia, Australia
  • David Thomas, Austin Health, Heidelberg, Victoria, Australia, Australia
  • Bridget Chappell, Austin Health, Heidelberg, Victoria, Australia, Australia
  • Christine Houlihan, Austin Health, Heidelberg, Victoria, Australia, Australia
  • Georgina Thomas, Austin Health, Heidelberg, Victoria, Australia, Australia
  • Richard MacIsaac, Austin Health, Heidelberg, Victoria, Australia, Australia
  • Sue Finch, Statistical Consulting Centre, University of Melbourne, Parkville, Australia
  • George Jerums, Austin Health, Heidelberg, Victoria, Australia, Australia

    • Objective: To measure and assess intraindividual reproducibility of 99mTc- MAG-3 clearance as a marker of effective renal plasma flow (ERPF) in subjects with type 2 diabetes. ERPF was measured pre and post administration of captopril to assess the activity of endogenous renin and angiotensin system in two groups of diabetic subjects, those with high (HDS) and low (LDS) habitual dietary salt intake.

    Methods: ERPF was measured 3-6 weeks post cessation of RAS interfering medications with and without administration of captopril (in random order). Following the injection of 10 MBq of 99mTc- MAG-3, radioisotope activity was measured from blood samples taken at 5, 10, 12, 15, 17, 20, 25, 30, 45, 60 and 90 minutes. A multisample, biexponential model was used to calculate 99mTc- MAG-3 clearance using Sigmaplot v 10.0. The results were analyzed using a multiple regression model.

    Results: The coefficient of variation of ERPF measurement was 3.8%. 15 subjects in LDS and 17 subjects in HDS had ERPF measured. There were no significant differences in the ERPF between the HDS and LDS (p=0.57) groups and administration of captopril versus no captopril (p=0.69). Multiple regression model confirmed that kidney length (p= 0.0002), age (p=0.01) and blood glucose level (p=0.03) were independent predictors of ERPF (R2= 0.65, p< 0.001) but not urinary sodium excretion (p=0.64).

    Conclusions: Kidney length, age and blood glucose level were independent predictors of ERPF. Habitual dietary sodium intake and the administration of captopril did not affect ERPF in this study.