Serum Metabolic Enzyme Activities and Hepatocyte Ultrastructure of Common Carp after Gallium Exposure

Abstract

Gallium (Ga) is one of the intermetallic elements increasingly being used in making high-speed semiconductors such as gallium arsenide. The purposes of this study were to investigate the effects of gallium on serum enzyme activities and on the ultrastructure of the liver in common carp (Cyprinus carpio). Common carp were exposed to 3 different sublethal levels of gallium (2.0, 4.0, and 8.0 mg/l) in laboratory toxicity tests. During a 28-d testing period, serum metabolic enzyme activity of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) was analyzed every 14 d. An increase of enzyme activity in serum was observed, particularly at the 2 highest exposure concentrations. Electron microscopy investigations revealed ultrastructural alterations in hepatocytes which were correlated with exposure concentrations and exposure time. Cytopathological effects included nuclei with irregular outlines and heterochromatin, fragmentation and vesiculation of endoplasmic reticula, and disruption of mitochondria. Moreover, proliferation of lysosomes with electron- dense bodies and lipid inclusions were also found in the cytoplasm of hepatocytes. Our results indicate that changes in metabolic enzyme activities in serum occurred; this fact was confirmed by ultrastructural observations during the exposure period. This study also emphasizes the importance of in vivo approaches to the assessment of relative compound effects and their potential hazards in aquatic animals.