INDEPENDENCE OF PHOSPHATE REABSORPTION AND GLOMERULAR FILTRATION IN THE DOG

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Abstract
The pres-sent study was initiated to determine whether the rate of re-absorption of phosphate is correlated with filtration rate, or whether it, like that of glucose, is fixed and limited. The question is one of importance for an understanding of the na- ture of the several renal mechanisms which stabilize the ionic pattern of the body fluids. Filtration rate was varied in 2 trained dogs over a range of roughly 2 fold by altering the protein content of the maintenance diet and the time following the last meal at which the expt. was performed. Neutral Na phosphate was infused at a rate sufficient to saturate the renal reabsorptive mechanism. Under these conditions it was found that the rate of reabsorption of phosphate expressed in millimols/min. was constant for each animal and independent of glomerular filtration rate. The phosphate reabsorptive mechanism is therefore basically dissimilar to those for chloride, bicarbonate and sodium. Generalizations concerning the reabsorption of ions are therefore unsound.