Effect of age on blood acid-base composition in adult humans.
Frassetto, F]lynda A., R. Curtis Morris Jr., Anthony Sebastian.
Lynda A. Frassetto, R. Curtis Morris Jr., Anthony Sebastian
APStracts 3:0144F, 1996.
In 64 apparently healthy adult humans (ages 17-74 years) ingesting
controlled diets, we investigated the separate and combined effects
of age, GFR (index of age-related renal functional decline), renal
net acid excretion (NAE, index of endogenous acid production [EAP]),
and blood PCO2 (PbCO2, index of respiratory set-point) on steady
-state blood hydrogen ion ([H+]b) and plasma bicarbonate concentration
([HCO3-]p). Independent predictors of [H+]b and [HCO3-]p were PbCO2,
NAE, and either age or GFR, but not both, because the two were highly
correlated (inversely). [H+]b increased with increasing PbCO2, NAE
and age, and with decreasing GFR. [HCO3-]p decreased with increasing
NAE and age, and increased with increasing PbCO2 and GFR. Age (or
GFR) at constant NAE had greater effect on both [H+]b and [HCO3-]p
than did NAE at constant age (or GFR). Neither PbCO2 nor NAE
correlated with age or GFR. Thus, two metabolic factors, diet
-dependent EAP and age (or GFR), operate independently to determine
blood acid-base composition in adult humans. Otherwise healthy adults
manifest a low-grade diet-dependent metabolic acidosis whose severity
increases with age at constant EAP, apparently due in part to the
normal age-related decline of renal function.
Received 6 May 1996; accepted in final form 30 July 1996.
APS Manuscript Number F132-6.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996