CYTOLOGICAL ALTERATIONS IN ISOLATED HEPATOCYTES FROM RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) EXPOSED INVITRO TO 4-CHLOROANILINE

In order to evaluate the suitability of ultrastructural criteria in isolated fish hepatocytes as endpoints in toxicological studies, liver cells isolated from rainbow trout (Oncorhynchus mykiss) by collagenase perfusion were exposed in vitro to sublethal concentrations (1, 3, 10 mg/l) of the reference toxicant 4-chloroaniline (4-CA) for up to 8 days. Cytopathological alterations in isolated cells were recorded after 1, 3 and 5 days and compared to hepatopathological effects induced by prolonged in vivo exposure of rainbow trout. Whereas trypan blue exclusion failed to reveal any effect of 4-CA exposure, cytological modifications could be detected as early as 1 day at 1 mg/l. Ultrastructural analysis unequivocally documented a complex set of sublethal effects in a dose- and time-dependent manner, including changes in all hepatocytic organelles. Evaluation and comparison of in Vitro results with hepatocellular effects in intact rainbow trout suggested major correspondence in some fundamental hepatocellular functions such as intracellular compartmentation, number of mitochondria and lysosomes, ultrastructural organization of the RER, as well as the secretory activity of the Golgi fields. Other symptoms, e.g., ER transformation into myelinated structures, most likely indicated toxicant-induced premature ageing of isolated hepatocytes. Apparent discrepancies between hepatocytic reactions in vivo and in vitro must be attributed to differential activation of metabolic pathways or the modulation of basic hepatocellular responses by external systemic factors.