Localization of phosphaturic effect of parathyroid hormone in nephron of the dog

Abstract

The renal mechanism and tubular site of the phosphaturic action of parathyroid hormone were investigated by clearance and stop-flow techniques in one intact and seven thyroparathyroidectomized dogs. Administration of hormone caused a significant increase in the excretion of phosphate without increasing the filtered load. Stop-flow analysis indicated that in the absence of parathyroid hormone most of the filtered phosphate was reabsorbed in the proximal tubule, and that the hormone increased the rate of phosphate excretion by inhibiting this reabsorptive mechanism. P 32 injected during stopped flow showed no significant transport across the renal tubule despite the presence of excess parathyroid hormone. Significant P 32 activity appeared in the stop-flow collections simultaneously with the appearance of new filtrate. There was no evidence that parathyroid hormone mediated a secretory process for phosphate excretion.