Diffusion and consumption of oxygen in the superfused retina of the drone (Apis mellifera) in darkness

Abstract

Double-barreled O2 microelectrodes were used to study O2 diffusion and consumption in the superfused drone (Apis mellifera) retina in darkness at 22°C Po2 was measured at different sites in the bath and retina. It was found that diffusion was essentially in one dimension and that the rate of O2 consumption (Q) was practically constant (on the macroscale) down to Po2s < 20 mm Hg, a situation that greatly simplified the analysis. The value obtained for Qwas 18 ± 0.7 (SEM) µl O2/cm3 tissue · min (n = 10), and Krogh’s permeation coefficient (αD) was 3.24 ± 0.18 (SEM) × 10-5 ml O2/min · atm · cm (n = 10). Calculations indicate that only a small fraction of this Q in darkness is necessary for the energy requirements of the sodium pump. The diffusion coefficient (D) in the retina was measured by abruptly cutting off diffusion from the bath and analyzing the time-course of the fall in Po2 at the surface of the tissue. The mean value of D was 1.03 ± 0.08 (SEM) × 10-5 cm2/s (n = 10). From αD and D, the solubility coefficient α was calculated to be 54 α 4.0 (SEM) µ1 02 STP/cm3 · atm (n = 10), ~1.8 times that for water. © 1981, Rockefeller University Press., All rights reserved.