Micropuncture Study of Inorganic Phosphate Excretion in the Rat *

Abstract

Micropuncture studies performed on normal and PO4-loaded rats indicate that the renal excretion of inorganic PO4 can be accounted for by processes of glomerular filtration and tubular reabsorption. No evidence for net tubular secretion of PO4 was obtained. In both groups of animals tubular reabsorption of PO4 takes place largely in the proximal convolution. The reabsorptive capacity of the proximal convolution for inorganic PO4 seems to be rate-limited and probably involves an active transport process.