Enzyme-histochemical studies of griseofulvin-intoxicated mouse livers.

Abstract

Enzyme-histochemical studies were conducted on livers of mice chronically fed griseofulvin (GF) in order to produce Mallory bodies (MBs) in hepatocytes. The development of MBs is associated with derangement of the immunohistochemically detectable intermediate filament (IF) cytoskeleton of the cytokeratin (CK) type, although no strict correlation between appearance or involution of MBs and the cytoskeletal alterations exists. Since the function of the IF cytoskeleton and the relationship of its disturbance to cell injury is unknown, the aim of the present study was to correlate the activities of several key enzymes of cellular metabolic pathways with the disturbance of the cytoskeleton architecture. For that purpose enzyme-histochemistry in combination with immunohistochemical CK-IF stainings were performed on identical sections. In GF-intoxicated mouse livers the normal topography of enzyme activities was disturbed, but no strict colocalization of enzymatic and cytoskeletal changes was found. Glucose-6-phosphatase, a microsomal enzyme involved in glucose output and gluconeogenesis, showed elevated activity in MB-free hepatocytes with diminished immunostainable CK-IF cytoskeleton refuting the concept of a disability of those cells to export glucose. It could indeed indicate that those cells without MBs are in the state of recovery. However, these cells could also resemble "hyperactive foci". Glycogen was decreased in MB-containing hepatocytes with disturbed cytoskeleton, and this feature favours the assumption of cell degeneration. On the other hand, the mitochondrial marker enzymes, i.e. succinate dehydrogenase, cytochrome-c-oxidase and 3-hydroxybutyrate dehydrogenase, remained unchanged in altered hepatocytes. Alkaline phosphatase activity at the canalicular pole of GF-intoxicated hepatocytes was elevated, indicating cholestatic features associated with this disorder. However, since altered hepatocytes did not show impairment of oxido-reductase activities, a severe impairment of bile secretion as a consequence of cell damage is unlikely. Unchanged or even increased ATPase activity of altered hepatocytes also indicated their sustained metabolic abilities. The results presented provide indirect evidence that hepatocytes with disturbed IF cytoskeleton do not significantly differ from normal cells with respect to oxidative metabolism, fatty acid synthesis and gluconeogenesis. This suggests that alterations of the IF cytoskeleton associated with GF intoxication and MB formation have no significant adverse influence on the metabolic functions of liver cells, as far as can be assessed by evaluation by enzyme-histochemical staining of several key enzymes.