Effects of intraluminal D-glucose and probenecid on urate absorption in the rat proximal tubule

Abstract

The in vivo microperfusion technique was employed to examine urate absorption in the proximal convoluted tubule of the rat kidney using [2-14C]urate as the marker for fractional urate absorption. With NaCl as the perfusion solution, water absorption averaged 2.53 +/- 0.16 nl.min-1.mm tubule-1, and the fractional absorption of [2-14C]urate averages 11.6 +/- 1.0%/mm tubule. The addition of D-glucose (50 mg/100 ml) enhanced water absorption to 3.62 +/- 0.19 nl.min-1.mm tubule-1, but inhibited fractional urate absorption to 6.6 +/- 1.2%/mm tubule. Phloridzin (4.4 mg/100 ml), 2-deoxy-D-glucose (45.6 mg/100 ml), and 3-O-methyl-D-glucose (53.9 mg/100 ml) also inhibited the absorption of [2-14C]urate to the same degree as did D-glucose despite differing effects on water absorption. The addition of probenecid (2.8 mg/100 ml) to the NaCl perfusion solution had no effect on water absorption but inhibited [2-14C]urate absorption to 6.4 +/- 0.6%/mm tubule. The addition of both probenecid and phloridzin further reduced [2-14C-A1urate absorption to 3.8 +/- 0.7%/mm tubule. Probenecid alone had no effect on glucose transport. These studies suggest that the presence of either certain hexose sugars, phloridzin, or probenecid in the lumen of the proximal convoluted tubule inhibits the tubular absorption of urate.