Ca(2+)-dependent nonspecific permeability of the inner membrane of liver mitochondria in the guinea fowl (Numida meleagris).

Abstract

This comparative study presents the results of the induction of Ca(2+)-dependent nonspecific permeability of the inner membrane (pore opening) of rat and guinea fowl liver mitochondria by mechanisms that are both sensitive and insensitive to cyclosporin A (CsA). It was established that energized rat and guinea fowl liver mitochondria incubated with 1mM of inorganic phosphate (Pi) are capable of swelling upon addition of at least 125 and 875nmol of CaCl2 per 1mg protein, respectively. Under these conditions, the Ca(2+) release from the mitochondria of these animals and a drop in Δψ are observed. All of these processes are inhibited by 1μM of CsA. FCCP, causing organelle de-energization, induces pore opening in rat and guinea fowl liver mitochondria upon addition of 45 и 625nmol of CaCl2 per 1mg protein, respectively. These results suggest the existence of a CsA-sensitive mechanism for the induction of Ca(2+)-dependent pores in guinea fowl liver mitochondria, which has been reported in rat liver mitochondria. However, guinea fowl liver mitochondria have a significantly greater resistance to Ca(2+) as a pore inducer compared to rat liver mitochondria. It was found that the addition of α,ω-hexadecanedioic acid (HDA) to rat and guinea fowl liver mitochondria incubated with CsA and loaded with Ca(2+) causes organelle swelling and Ca(2+) release from the matrix. It is assumed that in contrast to the CsA-sensitive pore, the CsA-insensitive pore induced by HDA in the inner membrane of guinea fowl liver mitochondria, as well as in rat liver mitochondria, is lipid in nature.