AJP - Regulatory, Integrative and Comparative Physiology, Vol 237, Issue 3 132-R138, Copyright © 1979 by American Physiological Society
Kinetics of bicarbonate/chloride exchange in dogfish erythrocytes
A. L. Obaid, A. M. Critz and E. D. Crandall
A stopped-flow rapid reaction apparatus was used to monitor changes in
extracellular pH in dogfish (Mustelus canis) erythrocyte suspensions under
conditions where dpH/dt was determined by the rate of HCO3-/Cl- exchange
across the red cell membrane. Experiments were performed on erythrocytes
suspended either in their own plasma or in elasmobranch Ringer solution
over a range of temperatures from 5 to 35 degrees C. The exchange fluxes at
25 degrees C for red blood cells suspended in their own plasma (2.03
nmol/cm2-s) or in Ringer solution (2.00 nmol/cm2-s) are not significantly
different and can be compared to those obtained under similar conditions
for human red cell suspensions (0.910 nmol/cm2-s). The flux for dogfish
erythrocytes suspended in Ringer solution was reduced by 80% after exposure
of the cells to SITS. An Arrhenius plot of the exchange rate constant
yielded an activation energy of about 13.2 kcal/mol. We conclude that 1)
plasma has no inhibitory effect of HCO3-/Cl- exchange across the dogfish
erythrocyte membrane or on activity of intraerythrocyte carbonic anhydrase,
2) HCO3-/Cl- exchange probably occurs via the same mechanism in fish and
mammalian erythrocytes, and 3) the conversion of plasms HCO3- to CO2 in
dogfish can be catalyzed by intraerythrocyte carbonic anhydrase.
