Effect of phosphate depletion on renal tubular reabsorption of glucose.

The renal handling of glucose was evaluated in six dogs before and after chronic phosphate depletion of 51 to 112 days' duration. Phosphate depletion was produced by feeding the dogs with phosphate-restricted diet and administration of Al(OH)3. With phosphate depletion, serum phosphate fell from 3.5 +/- 0.36 (S.E.) to 0.5 +/- 0.19 mg./dl. Both TmG and TmG/GFR fell significantly during phosphate depletion. TmG/GFR was 4.0 +/- 0.41 mg./ml. before phosphate depletion and 2.9 +/- 0.19 mg./ml. after phosphate depletion. In four phosphate-depleted dogs TmG/GFR fell precipitously after glucose loading for more than 200 minutes, and practically all of the filtered glucose was excreted in the urine. It is possible that the levels of cytosolic adenine nucleotides which are required for energy of the renal cell may be reduced during phosphate depletion. This may underlie the fall in TmG and may explain the precipitous fall in TmG when the transport mechanism for glucose was operating at maximum capacity for a prolonged period of time.