The effect of blood volume changes accompanying isotonic circumstances on plasma antidiuretic hormone levels in normal subjects.

Changes in plasma ADH levels were investigated in human male subjects whose blood volume was altered under isotonic circumstances. Blood volume was reduced by ambulation and increased by isotonic saline infusion in an overnight dehydrated state, and determinations were made on plasma ADH levels, plasma osmolality and hematocrit values. Plasma ADH levels were clearly affected by the small changes in blood volume, and significantly negative correlation was found between plasma ADH levels and the percent changes in blood volume under isotonic circumstances. From these findings, it was concluded that ADH release in human subjects is also controlled by the changes of the blood volume factor in addition to osmotic stimuli.