REDUCED OXYGENATION IN DIABETIC RAT KIDNEYS MEASURED BY T2*WEIGHTED MAGNETIC RESONANCE MICRO-IMAGING

By applying invasive techniques for direct measurements of oxygen tension, we have reported decreased kidney oxygenation in experimental diabetes in rats. However, the non-invasive MRI technique utilizing the BOLD effect provides several advantages with the possibility to perform repetitive measurements in the same animals and in human Subjects. In this study, we applied a modified single gradient echo microimaging sequence to detect the BOLD effect in kidneys of diabetic rats and compared the results to normoglycemic controls. All measurements were performed oil inactin-anaesthetized adult male Wistar Furth rats. Diabetes was induced by streptozotocin (45 mg/kg) 14 days prior to MRI-analysis. Sixteen T2*-weighted image records (B(0)=1.5 T) were performed using radiofrequency spoiled gradient echo sequence with 2.6 mls step increments of TE (TE(1)=12 ills), while TR (75 ms) and bandwidth per pixel (71.4 Hz) were kept constant. T2* maps were Computed by mono-exponential fitting of the pixel intensities. Relaxation rates R2* (1/T2*) in cortex and outer stripe of the outer medulla were similar in both groups (cortex for controls 22.3 +/- 0.4 vs. diabetics 23.1 +/- 1.8 Hz and outer stripe of outer medulla for controls 24.9 +/- 0.4 vs. diabetics 26.4 +/- 1.8 Hz; n=4 in both groups), whereas R2* was increased in the inner stripe Of the Outer medulla in diabetic rats (diabetics 26.1 +/- 2.4 vs. controls 18.8 +/- 1.4 Hz; n=4, P<0.05). This Study demonstrates that experimental diabetes in rats induces decreased oxygenation of the renal Outer medulla. Furthermore, the proposed T2*-weighted MR micro-imaging technique is Suitable for detection of regional changes in kidney oxygenation in experimental animal models.