Role of hydrolysis of membrane lipids of mitochrondria in their thyroxine-induced swelling

Swelling of mitochondria induced by thyroxine is accompanied by the accumulation of free fatty acids in the organelles; the level of these acids returns to its initial value during contraction of the mitochrondria in the presence of ATP. EDTA also causes contraction of the mitochondria, but without any corresponding utilization of fatty acids. Thyroxine-induced swelling of mitochondria is evidently due to activation of membrane phospholipase A2 and to an increase in permeability of the membranes to cations as a result of hydrolysis of phospholipids.