Abstract
Summary
Water, sodium, and potassium outputs increased well above control values in normal hydrated fasting dogs during the intravenous administration of isotonic saline solution. With the reduction in arterial pressure to a constant level close to 50 mm Hg by controlled hemorrhage in these animals, all three outputs decreased in association with diminished glomerular filtration rate (inulin clearance), hematocrit, and plasma protein concentration but never to levels as low as those observed during the control phase. Since the blood loss was more than replaced by the isotonic saline infused, it may be presumed that extracellular extravascular fluid volume increased while blood volume fell. The persistence of natriuresis indicates continued tubular rejection of sodium, possibly as a result of a change in interstitial volume or vascular perfusion of the kidney.
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