Nonparenchymal liver cells in a vertebrate without bile ducts.

The nonparenchymal portion of the liver of parasitic adult lampreys (Petromyzon marinus L.) consists of endothelial, Kupffer, fibroblast-like, fat-storing, and granulated cells. The fenestrae of endothelial cells are not organized into sieve plates but are of highly variable size and distribution. The dimension of some fenestrae suggests the possible transport of substances of large molecular size. Small numbers of Kupffer cells possess many features of these cells observed in other vertebrates but they do not have worm-like bodies and endogenous peroxidase activity. They are involved in erythrophagocytosis and perhaps the ingestion of other foreign material but they do not store iron. Fat-storing and fibroblast-like cells share many morphological features and may be different expressions of the same cell type. These perisinusoidal cells are rich in organelles suggesting protein synthesis but the fibroblast-like cells lack fat droplets. A cell with a large Golgi apparatus and associated cytoplasmic granules resembles the pit cell described in the liver of a few other vertebrates. The morphology of nonparenchymal cells of the liver in parasitic adult lampreys does not reflect the absence of bile ducts in this organism.