[In vitro maturation of rabbit reticulocytes: oxygen consumption reaction]

With a simple experimental system the changes of endogenous, antimycin A-suppressed, oligomycin-suppressed and antimycin A-resistant oxygen consumption are studied during the maturation of intact cells of the 6th day of bleeding. All functional characteristics of oxygen consumption decrease during maturation. The rate of decrease is strongly increased by high inorganic phosphate concentrations (125 mM). This effect is most obvious for the oligomycin-suppressed and the endogenous respiration. The degree of uncoupling of non-incubated cells is 14%. During 24 h incubation it rises to 75%. Inorganic phosphate accelerates the increase of uncoupling during maturation. Reticulocytes of the 4th day of bleeding are characterized by a higher respiratory capacity and also by a higher rate of maturation of antimycin A-suppressed and endogenous respiration. The degree of uncoupling does not increase during maturation. This may be attributed to the low lipoxygenase activity of these cells. 25% of the endogenous oxygen consumption of unmatured cells are antimycin A-resistant. This type of respiration declines by 50% in 4 h incubation irrespective of inorganic phosphate concentrations and day of bleeding. In nitrogen all functional characteristics of respiration during the maturation decline more rapidly than in oxygen. The antimycin A-resistant respiration, however decreased more slowly and reached 50% after 12 h. A pH dependence of maturation (maximum at pH 8.4) was found for the endogenous and the antimycin A-suppressed respiration. The degree of uncoupling rises most quickly at pH 7.4. This is possibly related to the pH maximum of lipoxygenase.