AJP - Regulatory, Integrative and Comparative Physiology, Vol 255, Issue 1 97-104, Copyright © 1988 by American Physiological Society
H+ homeostasis, osmolality, and body temperature during controlled NaCl and H2O intake
J. W. Anderson and D. B. Jennings
Department of Physiology, Queen's University, Kingston, Ontario, Canada.
Arterial PCO2, arterial [H+] ([H+]a), electrolytes, and osmolality, as well
as rectal temperature (Tre), were monitored in six awake dogs over
sequential 12- or 13-day periods in which their NaCl intake was first less
than 5 meq/day, then approximately 120 meq/day, and finally less than 5
meq/day. Water intake was maintained constant at 77 ml.kg-1.day-1
throughout. During low-NaCl periods, decreases in body and plasma water,
indicated by weight loss did not prevent lower arterial [Na+] ([Na+]a),
arterial [Cl-] ([Cl-]a), and osmolality relative to the high-NaCl period.
During high dietary NaCl, the arterial strong ion difference [[SID]a =
([Na+]a + [K+]a) - (arterial [lactate-] + [Cl-]a)] was lower. From
physicochemistry, this lowered [SID]a results in a higher [H+]a. However,
independent of NaCl intake, [H+]a was positively correlated with plasma
osmolality; moreover, [H+]a, relative to plasma osmolality, was higher at
lower Tre than at higher Tre. We speculate that this spectrum of plasma
osmolality and body temperature may contribute to the creation of an
appropriate protein pK to match plasma [H+]a. We also found that the
difference between plasma [protein] (measured by the biuret test) and
[ATOT]a (an estimation of plasma protein as total weak acid from
physicochemistry) was related to plasma osmolality, [SID]a, and [Na+]a.
These latter relations may reflect the effect of plasma water concentration
(osmolality) and strong ions on the pK of plasma proteins.
