Functional aspects of megamitochondria isolated from hydrazine- and ethanol-treated rat livers

It is essential to analyze functions of megamitochondria (MG) to elucidate the mechanism of the formation of MG induced under various pathological con ditions. The MG fraction obtained by a routine isolation procedure for norm al mitochondria always consists of a mixed population of mitochondria enlar ged to various degrees and also normal-sized ones. The purpose of the prese nt study is to answer the question of whether or not data obtained from the MG fraction consisting of such a heterogeneous population of mitochondria with respect to their sizes really reflect functions of MG. In the present study mitochondria were obtained from the livers of rats treated with a 1% hydrazine diet for 8 days and those given 32% ethanol In drinking water for up to 2 months using various isolation procedures. Results obtained are su mmarized as follows: (i) mitochondria enlarged to various degrees and norma l-sized ones are sometimes connected with each other by a narrow stalk in t he hepatocyte of hydrazine-treated animals, and such connections are mainta ined to some extent when mitochondria are isolated; and (ii) mitochondria o btained from experimental animals by a routine isolation procedure for mito chondria ((700-7000)gR(2)''') and those obtained by alternative isolation p rocedure yielding the heavy ((500-2000)gR(2)''') and light ((2000-7000)gR(2 )''') fractions show some functional similarities: decreases in the content of cytochrome a + a(3); decreases in oxygen consumptions and phosphorylati ng abilities; decreases in monoamine oxidase and cytochrome c oxidase activ ities; lowered membrane potential of mitochondria; decreases in the rate of the generation of reactive oxygen species. These results may suggest that mitochondria enlarged to various degrees and normal-sized ones are function ally similar to each other and that the MG fraction obtained by a routine i solation procedure for normal mitochondria can be applied to the study of t he function of MG.