AN ANTIDIURETIC MECHANISM NOT REGULATED BY EXTRACELLULAR FLUID TONICITY 12

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Abstract
Patients with inadequately treated Addison''s disease, certain cases of congestive heart failure who develop low serum Na concns. during treatment of their edema, and normal dogs depleted of extracellular fluid electrolyte show an abnormality of water excretion. This consists of a dilution of the serum but, in spite of this, a concd. urine and a failure to have a prompt water diuresis or dilution of the urine following admn. of, water. This antidiuretic pattern is reduplicated by continuous action of small amts. of posterior pituitary extract in normal dogs and man. It is considered at present that this abnormal antidiuretic pattern does represent a continued activity of the supraopticohypophyseal antidiuretic system in the presence of a dilute extracellular fluid which normally would inhibit its activity. It is suggested that the stimulus for posterior pituitary activity in the subject depleted of extracellular fluid electrolyte is an insufficiency of some function of volume in a crucial portion of the extracellular fluid volume, possibly intravascular.
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