Mitochondrial Oxidative Phosphorylation Controls SA-Induced Thermogenesis in the Appendix of Sauromatum Guttatum

Aim: To study thermogenesis induced by aspirin, salicylic acid and 2,6-dhdroxybenzoic acid in the appendix of the Sauromatum guttatm and Arum italicum inflorescences.

Study Design: Determination of tissue temperature in the presence of the three thermogenic inducers and mitochondrial inhibitors (antimycin, myxothiazol, salicylhydroxamic acid, 2,4-dinitrophenol, oligomycin and carboxyatractyloside).

Methods: Monitoring tissue temperature with thermocouples in the presence of inducers and different mitochondrial inhibitors over 48 h.

Results: Induced temperature rise was suppressed in the presence of different mitochondrial inhibitors. Inhibitors of complex III, Antimycin A (200 µM) and myxothiazol (200 µM), decreased significantly the rise in temperature independently of the inducer concentrations. Antimycin A (20 µM) combined with SHAM (2 mM), an alternative oxidase inhibitor, suppressed temperature rise. However, SHAM (2 mM) alone did not suppress the rise in temperature completely. An uncoupler, 2,4-DNP (1.5 mM) completely suppressed the rise in temperature. A diminished temperature rise was also detected in the presence of oligomycin (200 µM), an inhibitor of ATP synthase. Carboxyatractyloside, an adenine nucleotide translocator inhibitor, also suppressed the rise in temperature.

Conclusions: These results indicate that the SA-induced thermogenesis is depending on the mitochondrial oxidative phosphorylation. It may also suggest the existence of a second source of heat in the mitochondria that is SHAM-insensitive.