Low calorie commercial sugar is a sensitive marker of glomerular filtration rate.

BACKGROUND Glomerular filtration rate (GFR) in humans and animals might be determined with precision by measuring the clearance of an ideal marker, such as inulin. However, the use of inutest, an inulin analog, is limited by its cost and accessibility. The present study tested whether low calorie commercial sugar (LC sugar) can be used to measure GFR during normal and renal dysfunction. METHODS Two groups of 6 male Wistar rats weighing 300 to 350 g were included. One group was treated with a daily dose of cyclosporine (CsA) 30 mg/kg subcutaneously for 7 days and the other group was formed by nontreated control rats. In one half of each group, GFR was evaluated by using inutest and in the other half by using LC sugar. GFR was also evaluated by using a wide LC sugar plasma concentration range in an additional group. RESULTS In nontreated rats, the mean GFR evaluated with LC sugar was 2.2 +/- 0.1 mL/min. This value is equal to that obtained with inutest: 2.3 +/- 0.1 mL/min. CsA administration produced a significant reduction of renal blood flow and renal function. The GFR reduction induced by CsA was similarly determined by both LC sugar and inutest to be at 1.0 +/- 0.2 and 1.1 +/- 0.2 mL/min (P= NS), respectively. In addition, GFR did not change when LC sugar plasma concentration gradually increased. CONCLUSION Our results show that in both normal and pathophysiologic conditions, LC sugar is a good marker of GFR similar to the gold standard inutest.