Fine structure and surface adenosinetriphosphatase activity of a human hepatoma

A study has been made of the fine structure of a human hepatoma and of the subcellular distribution of its surface ATPase activity. Many cells showed close resemblances to normal liver parenchymal cells; organelles were polarized around structures resembling bile canaliculi, cisternae of rough-surfaced endoplasmic reticulum were well developed and glycogen stores were plentiful. Mitochondria were abnormal, showing swelling, pallor of the matrix, loss of dense granules and abnormal cristae. ATPase activity was present at the plasma membranes fronting adjacent tumor cells but was particularly prominent at the sites which resembled bile canaliculi, where its presence could be related to microvilli. The similarities in fine structure and localization of ATPase activity between this tumor and normal liver are discussed in relation both to other human and to experimental animal hepatomas, and their possible functional significance is considered.