AJP - Regulatory, Integrative and Comparative Physiology, Vol 250, Issue 2 260-R266, Copyright © 1986 by American Physiological Society
Studies on avian erythrocyte metabolism. XIV. Effect of CO2 and pH on P50 in the chicken
R. Isaacks, P. Goldman and C. Kim
The O2 affinity (P50) of erythrocyte suspensions from 18-day chick embryos,
from 2-, 5-, 8-, and 14-day chicks, and from mature chickens decreased with
increasing concentrations of either CO2 or H+, particularly at a pH near
7.4 and at 37 degrees C. A greater effect on delta P50's was observed from
increasing H+ concentration from pH 8.0 to 6.8 in cell suspensions from
18-day embryos (28.8 Torr at 0% CO2) and adult chickens (55.1 Torr at 0%
CO2) than from increases in CO2 concentration at any given pH. The Bohr
effect (delta log P50/delta pH) in the absence of CO2 was -0.508 and -0.479
for cell suspensions from 18-day chick embryos and adult birds,
respectively. The specific effect of CO2 on the Bohr effect, regardless of
the CO2 concentration, indicates that the delta P50/0.1 pH is approximately
1.35 and 2.45 Torr for the embryo and adult chicken blood. These results
indicate that increasing H+ and CO2 concentrations markedly affect the P50
of chicken blood and that even subtle changes in either could play a
significant role physiologically in regulating blood P50 in birds.
