Effects of extracellular fluid volume contraction and expansion on the bicarbonaturia of parathyroid hormone.

To evaluate the effect of extracellular fluid volume alterations on the bicarbonaturia of parathyroid hormone, thyroparathyroidectomized dogs were made alkalotic and volume-contracted or expanded through hemodialysis. Clearance studies were performed before and after infusion of purified bovine parathyroid extract (PTE). Glomerular filtration rate and blood bicarbonate concentrations were kept constant throughout the experiments. A significant increase in fractional bicarbonate excretion was observed following PTE infusion in both the volume-contracted (8.67 +/- 3.25 to 14.70 +/- 3.63%, P less than 0.010) and the volume-expanded state (22.80 +/- 3.04 to 37.26 +/- 3.38%, P less than 0.050). It is concluded that PTE decreases reabsorption of bicarbonate independent of the volume state of the animal.