Metabolism of antidiuretic hormones.

T HE RATE of change in the plasma concentration of antidiuretic hormone (ADH) is determined as much by the rate of removal of the hormone from the blood as it is by the rate of secretion into the blood [I]. It is evident, however, that in the control of osmolal concentration of the body fluids it is the secretory process that is the regulated variable. The removal process operates in a blind, continuous manner, clearing ADH from a more or less constant fraction of the plasma volume each minute, whether the plasma concentration is high or near zero. In this view, change in clearance modifies only the time required for correction of a disturbance in plasma osmolal concentration but does not affect the value at which osmolal concentration stabilizes [Z]. It is also evident that the removal process in the responsible organs must be subject to controls, but only a beginning has been made toward understanding the metabolic factors involved. Even the effect of change in as obvious a factor as blood flow through such an organ has been examined in only a few studies.