High-voltage electron microscopy of adrenal medulla: direct connections between mitochondria and catecholamine-storage vesicles.

A high-voltage electron microscopic study of adrenal medullary cells from hypoglycemia-stressed rats revealed the existence of tubular channels which create a luminal continuity between the mitochondrial compartment and the catecholamine-storage vesicles. It is suggested that these channels allow for the transfer of materials such as high-energy nucleotides between the mitochondria and the catecholamine-storage vesicles without an intervening membrane.