Trapping of electro-injected [14C]sucrose by hepatocyte mitochondria: a mechanism for cellular autofiltration?

[14C]Sucrose was introduced, by means of electropermeabilization, into the cytosol of isolated rat hepatocytes to serve as an inert marker of the intracellular fluid. Radioactivity accumulated in mitochondria (as well as in lysosomes) at a rate of 2-3%/h for 4 h of incubation at 37 degrees C, as shown by subcellular fractionation in isotonic density gradients. This unprecedented mitochondrial trapping of a molecule which does not cross most biological membranes points to the possibility that mitochondria participate in some kind of autofiltration of cellular fluid.