Inhibition by volume expansion of phosphate uptake by the renal proximal tubule brush border membrane.

Clearance studies and examination of brush border membrane (BBM) vesicle transport were performed in rats that had been volume expanded by 10% of body weight. The results were compared to those obtained in control animals. The data indicate that the phosphaturia which resulted from the expansion procedure was accompanied by an inhibition of proximal BBM phosphate uptake. The BBM uptake of proline and glucose was unchanged. Furthermore, since plasma calcium did not change, the findings are compatible with the view that the membrane transport changes resulted from alterations induced by the saline loading itself, rather than (or in addition to) any changes caused by parathyroid hormone excretion.