Journal of Applied Physiology, Vol 43, Issue 6 925-930, Copyright © 1977 by American Physiological Society
Determinants of transmembrane bicarbonate flux during acid-base changes
D. R. Strome, R. L. Clancy and N. C. Gonzalez
Experiments were designed to determine the contribution of increased
extracellular HCO3- concentration, [HCO-3e], to the net
extracellular-to-intracellular HCO3- flux observed in hearts during
hypercapnia. Isolated rabbit hearts were perfused by recirculating for
15-min periods a small volume of Ringer solution in which [HCO-3e] and
carbon dioxide tension (PCO2) could be independently altered. A net HCO-3
flux was evidenced by a decrease in [HCO-3e] during recirculation. [HCO-3e]
was randomly increased from 19 mM over a range of 19-42 mM at a constant
PCO2 of 38.7 Torr. The resulting flux increased linearly with the [HCO-3e]
existing at the start of recirculation. The same relationship was observed
at 95.8 Torr PCO2. The disappearance of HCO-3 from the perfusate could not
be explained by dilution in the interstitium or by lactate accumulation.
When PCO2 was increased from 40 Torr over a range of 40-160 Torr at a
constant [HCO-3e] of 20 or 30 mM, a small flux was observed only at the
highest PCO2 levels. Essentially the same results were obtained when
recirculation time was prolonged to 30 min. These results suggest that the
major determinant of the HCO-3 flux is a change in extracellular HCO-3
concentration.
