IMMUNOELECTRON MICROSCOPIC STUDY OF THE DISTRIBUTION OF PORIN ON OUTER MEMBRANES OF RAT-HEART MITOCHONDRIA

The distribution of porin on the outer membranes of rat heart mitochon dria has been studied by means of immunogold labelling with antibodies to the N-terminal part of the human protein. It was found that only a minority of isolated, unfixed mitochondria are labelled by these anti bodies, with the gold particles frequently organized in threads or ban ds. Extensive immunogold labelling is frequently observed on regions o f outer membranes stripped away from mitochondria and on regions separ ating two mitochondrial compartments whose cristae display different c onfigurations (possibly representing two mitoplasts covered by a commo n outer membrane). Also, pairs of connected mitochondria are sometimes heavily labelled in the ''neck'' regions, which may represent the jun ctions involved in electrical communication between mitochondria in ca rdiac tissue.