Oxygenation and deoxygenation kinetics of red cells in isolated lamellae of fish gills.

1. The kinetics of oxygen transfer across the water-blood barrier in fish gills were studied by measuring oxygenation and deoxygenation of single red blood cells contained within isolated secondary lamellae using a microphotometric technique. 2. Recordings of the overall time courses show that both oxygenation and deoxygenation are more rapid in the carp than in the eel. In both species the half-time for deoxygenation is about five times slower than for oxygenation. 3. It is shown that the resistances to oxygenation and deoxygenation are identical; the differences in the shapes of the O2 v. time curves recorded being attributable to the influence of the HbO2 dissociation curve upon the driving force for diffusion. 4. It is concluded that a diffusional as opposed to a chemical reaction resistance provides the main barrier to oxygen transfer in gill secondary lamellae.