OSCILLATING CA2-INDUCED CHANNEL ACTIVITY OBTAINED IN BLM WITH A MITOCHONDRIAL-MEMBRANE COMPONENT()

Oscillations in ion fluxes and membrane potential may be observed in c ells and in mitochondria as well. We obtained Ca2+-induced oscillation s in channel activity in black-lipid membranes reconstituted with hydr ophobic components extracted from mitochondria. Mitoplasts prepared fr om purified rat liver mitochondria were extracted with ethanol followe d by Folch extraction and further partial purification by silicic acid chromatography. Channel activity was measured in lipid bilayers forme d from bovine brain lipids and 10% cardiolipin with addition of the pu rified fractions. The conductance with 10 mM Ca2+ was 100 pS or its mu ltiples. Ca2+ gradients of 4:1 induced. oscillating channel activity f or several hours, with initial open states of 40 s and closed states o f 56 s; the open times gradually decreasing to 8.6 s. No channel activ ity was seen without added fractions. The channel activity was associa ted with a Ca2+-binding lipid, nonpolar, low-molecular-weight fraction that in gel electrophoresis was not stained with Coomassie Blue and d id not contain carbohydrate-staining material. H-1-Nuclear magnetic re sonance spectra of the substance showed the presence of aliphatic chai ns and carbonyls, but the detailed structure remains to be elucidated.