ABSTRACT: The 4-quinolone antibacterials oxolinic acid and flumequine are routinely and successfully used in commercial aquaculture. In order to investigate the effects of these antibiotics on fish liver ultrastructure, rainbow trout were fed diets containing oxolinic acid or flumequine at concentrations of 1.0 and 1.2 g kg^-1 food, respectively, at a ration of 1% body weight d^-1 for 10 d. Fish were sampled for examination on Days 1 and 10 after a return to normal diet and hepatic ultrastructural alterations were quantified by stereological analysis. Both drugs induced an almost 2.5-fold increase in the volume of the rough endoplasmic reticulum, which displayed phenomena of dilation, vesiculation and fragmentation. Glycogen deposits were depleted to approximately 50% of their control volume accompanied by the formation of clusters of lipid droplets. Additional structural alterations included the intralysosomal accumulation of stacked membranes and the presence of elaborated myelin figures interspersed in the cytoplasm. No drug-specific responses were observed. In general, compensatory rather than degenerative changes followed the antibiotic administration. Further signs supporting a stimulation in the hepatocellular metabolic activity were mitochondrial hyperplasia after flumequine administration and high nuclear-cytoplasmic ratios in individuals treated with oxolinic acid.

KEY WORDS: Antibiotics · Oxolinic acid · Flumequine · Rainbow trout · Liver · Ultrastructure

Published in DAO Vol. 29, No. 1 (1997) on April 24
ISSN: 0177-5103. Copyright © Inter-Research, Oldendorf/Luhe, 1997