Abstract:

Isolated rat liver mitochondria were proposed as a model to monitor real-time heat metabolism.A high-throughput and sensitive thermal activity monitor Ⅲ (TAM Ⅲ) was used to detect the P-t curves of mitochondria under different conditions, including different mitochondrial concentrations, different substrates, different buffers, respiratory inhibitors, Ca²⁺, and CsA.We determined the thermokinetic parameters through calculation.The results showed that:(1) higher concentration of mitochondria led to faster energetic metabolism; (2) when succinate was the direct respiratory substrate, it promoted mitochondrial metabolism, in contrast to the condition when an indirect substrate, pyruvate, was used; (3) high concentration of Ca²⁺(2.5 mmol·L^-1) stimulated mitochondrial metabolism, however CsA, an inhibitor of mitochondrial permeability transition pores, could not reverse the Ca²⁺-induced mitochondrial alteration; (4) mitochondria in various buffers displayed different rates of heat metabolism, because of the different composition of the buffers; (5) mitochondrial metabolism was inhibited by respiratory inhibitors, especially NaN₃, which is an inhibitor of Complex Ⅳ and which completely stopped the mitochondrial heat release.

Key words: Mitochondria, Microcalorimetry, Metabolic rate, Respiratory inhibitor, Mitochondrial permeability transition