ULTRASTRUCTURAL AND FUNCTIONAL-STUDY OF THE LIVER PIGMENT-CELLS FROM RANA-ESCULENTA L

A study of the liver pigment cells of Rana esculenta L. has been perfo rmed on both liver in tote and cells in culture. Ultrastructural and c ytochemical analyses showed a close relationship between this visceral pigment cell system and the cells of hepatic macrophage lineage. Like the latter, the liver pigment cells present phagocytic activity, in t he sinusoids and in vitro, and give a positive response to tests for p eroxidase and lipase. The liver pigment cells are isolated, together w ith the Kupffer cells, from the sinusoidal cell fraction of the liver. In culture, they maintain their melanogenetic ability, demonstrated b y the presence of dopaoxidase activity in the soluble, membranous, and melanosome fractions. Analysis of the cultures showed that as culture time increased, so did melanosome dopaoxidase activity, the number of pigmented fields; and the level of pigmentation of the cells. The val ues of dopaoxidase activity of the pigment cells in culture show the s ame seasonal oscillations as the system in tote, indicating that the c ells maintain an internal clock, at least in the first 72 h of culture . There is evidence that the pigment cells are macrophages which can e xpress a melanogenetic function. Our results and other experimental da ta provide a basis for hypothesizing that the pigment cells in Rana es culenta L. liver may derive from, or have a common origin with, the Ku pffer cells.