Calcium ion activation of the anion‐conducting channel in the rat liver mitochondrial inner membrane

Abstract

Stimulation of the rat liver mitochondrial inner-membrane anion-conducting channel by aeration is dependent on the concentration of Ca2+ ions in the assay medium. Ca2+ activates anion conduction in both aerated and non-energised mitochondria but acts over a wider concentration range *+ and produces a greater increase in anion-conductivity in aerated mitochondria. EGTA reverses Ca stimulation but takes several seconds to act, *+ indicating slow release of Ca from the activation site possibly on the matrix side of the inner mitochondrial membrane. It is suggested that this channel may respond to hormone-induced changes in cytosolic Caz+ concentration.

GOLAC: An Endogenous Anion Channel of the Golgi Complex

“…The strongest argument that GOLAC is a Golgi channel is that no other channel with the properties of GOLAC has previously been described by others in recordings from endoplasmic reticulum (Simon and Blobel, 1991;Morier and Sauve, 1994;Duncan et al, 1997;Eliassi et al, 1997;Schmid et al, 1988), sarcoplasmic reticulum (Townsend and Rosenberg, 1995;Hals et al, 1989;Rousseau, 1989), or lysosomal fractions (Tilly et al, 1992). In addition, none of the single channels recorded from liver (the tissue source for our studies) were similar to GOLAC (plasma membranes (Henderson et al, 1989;Sellinger et al, 1992), organelles (mitochondria; Bowen et al, 1985;Costa et al, 1991;Selwyn et al, 1990), and peroxisomes (Labarca et al, 1986;Lemmens et al, 1989)). Second, the enrichment for Golgi markers in the cycloheximide Golgi fraction is orders of FIGURE 7 Conductance increased when lumenal pH was reduced.…”

The pH‐dependent anion‐conducting channel of the mitochondrial inner membrane is potently inhibited by zinc ions

“…were prepared from the hvers of adult Wistar rats as described previously [16,21] with 0.5 mM EGTA in the homogenisation and first wash media.…”

“…The anion uniport was assayed by light scattering changes produced by passive osmotic swelling of mitochondria suspended in ammonium salt media m the presence of rotenone, antlmycm A and FCCP with controls in the absence of FCCP as described previously [16]. For some experiments, mitochondrla were depleted of Ca'+ and Mg'+ by the method of Beavis and Garlid and assayed in KC1 mecha [17].…”