Abstract 1495: Existence of Hyperfiltration in an Early Diabetic Rat was Visualised by Multiphoton Microscopy
To visualise glomerular filtration under physiological conditions in an early diabetic rat and to evaluate filtration molecularly and quantitatively. We used 4 week STZ (50 mg/kg) model as early diabetic rats. We measured diameters of afferent (aff) and efferent (eff) arterioles, glomerular red blood cell velocities and left renal blood flow with our intravital videomicro-scope. Glomerular filtration was visualised by multiphoton microscopy. Various sizes of dextran (3k, 10k, 40k and 70k dalton (Dal)) conjugated with Texas Red in 0.5 ml were administered intravenously by bolus shot and for the next 60 seconds glomerular filtration was observed. FITC conjugated 500k Dal dextran was administered to dye intravascular area. The time course of Texas Red intensity in Bowman’s space was measured from the recorded images. Intensity peak values were normalized by the peak value of 3k Dal as sieving coefficients since the intensity reached its peak within 10 seconds after administration of Texas Red conjugated dextrans. Afferent arteriolar diameters were larger than efferent arteriolar diameters in both control (n=6) and diabetic (n=7) rats. Increases of both afferent and efferent diameters were remarkable in diabetic rats (p<0.05) (aff/eff diameter, DM rats: 14.0 ± 1.9, 9.4 ± 0.7, Control rats: 11.9 ± 0.8, 8.8 ± 0.7 μm). Glomerular red blood cell velocity in diabetic rats was larger than that in control rats (p<0.05) (DM/Control rats: 0.236 ± 0.030, 0.196 ± 0.076 mm/s). Left renal blood flow in diabetic rats was larger than that in control rats (p<0.05) (DM/Control rats: 1.84 ± 0.16, 1.60 ± 0.17 ml/100 gBW). All of these findings suggest the existence of hyperfiltration in early diabetic rats. In fact, filtration of the larger dextrans (40k and 70k Dal) were clearly visualized by multiphoton microscopy in early diabetic rats indicating greater leakage even from the early stage of diabetes with a significant difference by about 20% for the 40k and 70k Dal sieving coefficients comparing with the control group (p<0.05). Both afferent and efferent arteriolar diameters were increased in early diabetic rats suggesting the existence of hyperfiltration and the hyperfiltration was clearly visualised by multiphoton microscopy.