A Comparison of the Relative Effectiveness of Hydropenia and of Pitressin® in Producing a Concentrated Urine12

It is a common assumption that exogenous anti- diuretic hormone (Pitressing) is equal to the endogenous anti-diuretic hormone (ADH) in its ability to stimulate the production of a concen- trated urine.However, clinical studies of urine formation after the administration of Pitressin'S or Pituitrin@ leave some doubt as to the ability of the exogenous hormone to produce a maximally concentrated urine.Sodeman and Engelhardt (1) found that if urinary specific gravity was low at the time of Pituitrin0 administration, the value attained was not so high as could be produced in the same subject by water deprivation.Similar observations were made by Little, Wallace, What- ley, and Anderson (2).Taylor, Peirce, and Page (3) gave Pituitrin@ at frequent intervals for 12 hours and found the urine to be often more dilute and of larger volume than after a 12-hour period of water deprivation.In every case the amounts of anti-diuretic hormone administered were much greater than are assumed to be normally produced.In the present study the ability of exogenous anti-diuretic hormone, administered as Pitressin@, to concentrate the urine has been reinvestigated in humans and in the dog.Because it is now rec- ognized that the concentration of urine depends not only on the degree of hydropenia, but also on the prevailing rate of solute excretion (4-6), it seemed pertinent to investigate urinary concen- 1 This investigation was supported in part by a re- search grant (H-1638) from the National Heart In- stitute of the National Institutes of Health, United States Public Health Service.