Possible involvement of endogenous free fatty acids in the selective inactivation of the mitochondrial electron transfer system during hyperthermic incubation of rabbit reticulocytes.

Preincubation of rabbit reticulocyte-rich red cell suspensions at 45 degrees C for 1 h led to a lowering of the total endogenous oxygen uptake by 40%, a decrease of the CCCP-stimulated antimycin-A-sensitive part of the oxygen uptake by 72%, an inhibition of the antimycin A-resistant oxygen uptake by only one-third, the loss of the response of cell respiration to the uncoupler CCCP and a slight enhancement of the degree of uncoupling which is however of minor importance for the changes in the cell respiration during hyperthermic incubation. The degree of inactivation of the respiratory chain increased continuously with the temperature of preincubation beginning at 39 degrees C. Addition of defatted human serum albumin to the cells caused protection from thermal inactivation. The protective action of serum albumin was lowered by loading it with myristic acid. It is concluded that the thermal inactivation of the respiratory chain in reticulocytes may be mediated by endogenous free fatty acids.