The GSC of albumin and 69-kD FITC-dextran is unchanged in 12-wk diabetic versus control rats. (A) GSC of albumin-Alexa568 in 12-wk diabetic and aged-matched control rats demonstrates no significant change in the GSC for albumin (control n = 4, diabetic n = 4; 13 data points for control animals and 13 data points for diabetic animals over 24 min). (B) GSC of 69-kD FITC-dextran in 12-wk diabetic and aged-matched control rats demonstrates no significant change in the GSC for dextran, confirming the results obtained for albumin GSC (control n = 4, diabetic n = 5; 16 data points for control animals and 12 data points for diabetic animals taken over 24 min). (C) The plasma clearance of albumin-Alexa and 69-kD FITC-dextran over 24 h demonstrates that dextran is quickly cleared from the plasma over 24 h but a large portion of albumin is retained in the plasma despite the two molecules’ having similar GSC (albumin n = 4, dextran n = 4). (D) Representative pictures showing before and 24 min after injection of green 69-kD FITC-dextran (top) and red albumin-Alexa568 (bottom) in 12-wk control rats. Albumin (red) can be seen distributed in PT cells, whereas dextran (green) uptake is negligible. Bar = 30 μm. G, glomerulus; PT, proximal tubule.