AJP - Regulatory, Integrative and Comparative Physiology, Vol 232, Issue 5 145-R149, Copyright © 1977 by American Physiological Society
Control of extracellular sodium concentration by antidiuretic hormone-thirst feedback mechanism
D. B. Young, Y. J. Pan and A. C. Guyton
The effectiveness of the antidiuretic hormone (ADH)-thirst feedback
mechanism to control extracellular sodium concentration was studied in
dogs. The design consisted of increasing daily sodium intake from 10 to 200
meq in a group of dogs, first in the normal condition and second with a
continuous 24 h/day infusion of an amount of ADH sufficient to maintain
urine osmolarity at a maximal level and with fixed water intake. We were
therefore able to compare the effectiveness of sodium concentration control
in the same dogs with and without feedback control of the ADH-thirst
mechanism, the difference in effectiveness being a quantitative measure of
the control capability of the system. In the normal condition the increase
in sodium intake resulted in a steady-state 2.3% elevation in sodium
concentration. With the feedback control of ADH secretion and water intake
blocked, the same sodium forcing produced an 11.9% increase in
extracellular sodium concentration. The minimum feedback gain for the
system calculated from the data is -4.2. We conclude that control of sodium
concentration in the intact state is accomplished mainly by the ADH-thirst
feedback mechanism.
