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

This comparative study presents the results of the induction of Ca^sup 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 1 mM of inorganic phosphate (P^sub i^) are capable of swelling upon addition of at least 125 and 875 nmol of CaCl^sub 2^ per 1 mg protein, respectively. Under these conditions, the Ca^sup 2+^ release from the mitochondria of these animals and a drop in Δψ are observed. All of these processes are inhibited by 1 [mu]M of CsA. FCCP, causing organelle de-energization, induces pore opening in rat and guinea fowl liver mitochondria upon addition of 45 и 625 nmol of CaCl^sub 2^ per 1 mg protein, respectively. These results suggest the existence of a CsA-sensitive mechanism for the induction of Ca^sup 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^sup 2+^ as a pore inducer compared to rat liver mitochondria. It was found that the addition of [alpha],[omega]-hexadecanedioic acid (HDA) to rat and guinea fowl liver mitochondria incubated with CsA and loaded with Ca^sup 2+^ causes organelle swelling and Ca^sup 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.