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Abstract

Tubular free flow micropuncture studies were done in normoglycemic rats to evaluated-glucose handling along the nephron.
1. A rapid removal of filtered glucose occured over the first three millimeters of the proximal tubule.
2. The intratubular glucose concentration remained constant at 0.25±0.20 mmol/l (SD) over the second half of the accessible proximal tubule. This value is similar to one predicted on the basis of kinetic data obtained previously under conditions of zero volume flux.
3. More than 98 per cent of the filtered glucose was reabsorbed by the proximal tubule.
4. No further net flux was detectable between the proximal segment and the end of the distal tubule accessible to micropuncture.
5. The collecting duct reduced glucose excretion to less than 0.1 per cent of the filtered load. The final rate of glucose excretion was independent of the rate of urine flow.