Record Details

Yacoe, Marshall E
Effects of temperature, pH, and CO2‚ tension on the metabolism of isolated hepatic mitochondria of the desert iguana, Dipsosaurus dorsalis
Physiological Zoology
Journal Article
Dipsosaurus dorsalis
Mitochondria were isolated from the liver of the desert iguana, Dipsosaurus dorsalis. The kinetics (Km, Vmax.) of succinate oxidation by these mitochondria were determined at 25°C and 40°C over a range of pH values (6.5-7.5) and CO2 tensions (0.2-41 torr). Mitochondrial succinate oxidation was very closely described by Michaelis-Menten kinetics. Vmax varied directly with temperature but was not affected by variation of either pH or PC02. Apparent Km for succinate was affected by pH and Pco2 as well as temperature, varying directly with pH and Pco2 but inversely with temperature. The effects of temperature on Km for succinate were minimized when mitochondria were incubated in media whose pH and Pco2 approximated in vivo intracellular values. The Q10 values were calculated for three different acid-base regulatory patterns over a wide range of substrate concentrations. The data support the hypothesis that the desert iguana's normal acid-base regulatory pattern serves to minimize the effect of temperature on mitochondrial metabolism. The results, however, cannot be explained solely in terms of temperature/acid-base effects on the ionization state of protein-bound dissociable group.