AJP - Renal Physiology, Vol 248, Issue 4 492-F499, Copyright © 1985 by American Physiological Society
Adaptive changes in renal acidification in response to chronic respiratory acidosis
R. L. Tannen and B. Hamid
To examine whether chronic respiratory acidosis results in adaptive changes
in renal acidification, rats were housed for 3 days in an environmental
chamber with an ambient CO2 content of 10% and their kidneys were perfused
in vitro according to two protocols. To assess hydrogen ion secretory
capacity of the distal nephron, perfusions were carried out with a low
bicarbonate concentration, in the absence of ammoniagenic substrate, and
with saturating quantities of the buffer creatinine. Under these
conditions, the titration of creatinine at a pH less than 6.0 (TA pH 6.0)
reflects the H+ secretory capacity of a discrete functional segment of the
distal nephron. Kidneys from rats with chronic respiratory acidosis
exhibited a significantly lower urine pH and higher rate of TA pH 6.0 than
controls perfused in this fashion, indicative of an adaptive increase in
the distal nephron capacity for proton transport. This adaptation was
comparable with that reported previously for rats exposed to chronic
metabolic acidosis. Furthermore, evidence of adaptation persisted in the
presence of amiloride (10(-5) M), suggesting that it reflects, at least in
part, a sodium-independent mechanism of proton transport. Hydrogen ion
secretion by the proximal nephron was assessed by performing standard
bicarbonate titration curves with kidneys from rats with chronic
respiratory acidosis, chronic metabolic acidosis, and controls using a
perfusate equilibrated with 95% O2/5% CO2.(ABSTRACT TRUNCATED AT 250 WORDS)
