The temperature dependence of State IV respiration, the calcium uptake system, and the activity of the calcium ionophore A23187 in mitochondria from endo- and ectothermic animals.
1. Arrhenius plots of State IV respiratory activity of liver mitochondria from both rainbow trout and rat were linear over the temperature range 5-35 degrees C. 2. Calcium uptake was monitored by stimulation of oxygen consumption and by calcium electrode recording, with quite comparable results. Rainbow trout gave the usual linear Arrhenius plot but this plot for rat mitochondria exhibited two well-defined inflections or discontinuities. 3. The temperature dependence of the activity of the ionophore A23187 was investigated by measuring the increase in oxygen uptake following a sub-maximal dose of this drug. Again a linear relation was found for rainbow trout, but in this case the rat curves showed only a single inflection point. 4. These results are discussed in relation to other work on the effects of lipid phase transitions on mitochondrial membrane-associated systems.
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D010101:Oxygen Consumption; D051381:Rats; D013045:Species Specificity; D013696:Temperature
D000001:Calcimycin; D002118:Calcium