Journal of Applied Physiology, Vol 47, Issue 5 1079-1083, Copyright © 1979 by American Physiological Society
Postcapillary pH disequilibrium after gas exchange in isolated perfused liver
J. E. O'Brasky, T. Mauro and E. D. Crandall
pH equilibration after gas exchange in a systemic vascular bed was
investigated using an isolated guinea pig liver preparation perfused with a
blood-free Krebs-Ringer-bicarbonate solution. Effluent perfusate was
withdrawn into a stopped-flow apparatus in which pH and temperature were
continuously monitored. A decrease in pH of the perfusate after exit from
the liver was observed. Addition of acetazolamide to inflowing perfusate
had little effect on this fall in effluent fluid pH, while the addition of
carbonic anhydrase completely abolished the decrease in pH. These results
suggest that: 1) after the addition of metabolically produced CO2, the
reaction CO2 leads to H2CO3 leads to H+ + HCO3- in the perfusate did not
reach equilibrium during passage through the liver; 2) acetazolamide had
little effect on the magnitude of the pH disequilibrium; and 3) carbonic
anhydrase accelerated the reaction to equilibrium. We conclude that little
or no catalysis of the conversion of perfusate CO2 to H2CO3 takes place
within the hepatic circulation and that the presence of slow postcapillary
blood pH changes in vivo may be dependent on the specific species and organ
vascular bed from which the blood exited after participating in gas
exchange.
