
localization of phosphaturic effect of
parathyroid hormone in nephron of the dog
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.  p32 injected during stopped flow showed no significant
transport across the renal tubule despite the presence of
excess parathyroid hormone.  significant p32 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.
