Study on Biological Effects of La3+ on Rat Liver Mitochondria by Microcalorimetric and Spectroscopic Methods

The effects of lanthanum on heat production of mitochondria isolated from Wistar rat liver were investigated with microcalorimetry; simultaneously, the effects on mitochondrial swelling and membrane potential (Delta psi) were determined by spectroscopic methods. La3+ showed only inhibitory action on mitochondrial energy turnover with IC50 being 55.8 mu mol L-1. In the spectroscopic experiments, La3+, like Ca2+, induced rat liver mitochondrial swelling and decreased membrane potential (Delta psi), which was inhibited by the specific permeability transition inhibitor, cyclosporine A (CsA). The induction ability of La3+ was stronger than that of Ca2+. These results demonstrated that La3+ had some biotoxicity effect on mitochondria; the effects of La3+ and Ca2+ on rat liver mitochondrial membrane permeability transition (MPT) are different, and La represents toxic action rather than Ca analogy.