RENAL TUBULAR REABSORPTION OF UREA IN SHEEP

¹ Physiology Department, Rowett Research Institute, Bucksburn, Aberdeen, AB2 9SB

Renal tubular reabsorption of urea was studied in sheep fed diets containing either 2·7 or 0·88 per cent nitrogen but which were equal in the proportions of roughage to concentrate components and in energy.

As the amount of urea filtered at the glomerulus increased through the range 54-1347 µmole/min the amount reabsorbed by the tubule increased proportionately. This relationship was not influenced by urine flow rate within the range 1·0-9·2 ml./min. At urine flow rates less than 1·0 ml./min percentage reabsorption of filtered urea increased as urine flow rate diminished, an effect which was more marked when the low-N diet was fed compared to when the high-N diet was fed. This difference did not appear to be related to differences in the absolute amount of urea filtered but rather to differences in nitrogen intake or metabolism. The mechanism by which reabsorption is increased is as yet uncertain.

Note:

The authors would like to thank Mr W. Buchan for skilled technical assistance during these experiments.