EFFECT OF CHRONIC PITRESSIN ADMINISTRATION ON ELECTROLYTE EXCRETION IN NORMAL DOGS AND IN DOGS WITH EXPERIMENTAL ASCITES

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Abstract
Effects of chronic Pitressin administration (1-2.5 units of Pitressin tannate in oil twice daily) were studied in 2 normal dogs, 2 dogs with ascites produced by thoracic inferior vena cava constriction, and 2 adrenalectomized dogs with thoracic inferior caval constriction and ascites. Water retention was apparently the primary action; this effect and the subsequent changes occurred only when water was given by stomach tube in addition to voluntary intake. After 3-5 days of fluid retention, water excretion increased and no further expansion of the volume of plasma and extracellular fluid occurred. A striking hyponatremia resulted. A marked increase in GFR and RPF occurred in all but 1 dog (an adrenalectomized animal). In the 2 normals, a natriuresis and kaluresis resulted but in the dogs with ascites and intact adrenal cortices Na excretion remained low or decreased further while fecal K out-put increased. In the adrenalectomized dogs with ascites, Na and K excretion was unaltered during maintenance on 1 mg/day of DCA. When water intake was limited to drinking in the 2 normal animals, no changes in electrolyte excretion were de-tected; this indicates that Pitressin had no direct effect on renal tubular transport of electrolytes.