Effect of Lead Nitrate on the Liver of the Cichlid Fish (Oreochromis niloticus): A Light Microscope Study

Abstract

The adverse impacts of heavy metals on fish liver were evident with great variability among organs and species. The present study deals with the histological changes of the hepatocytes of the Nile tilapia, Oreochromis niloticus, following exposure to 2.5, 5, 10 ppm of lead nitrate for 1, 2, 3, 4 weeks. The present results revealed that lead nitrate exerts some histological effects on the hepatic tissue after exposure to the first concentration in the form of dilatation and congestion of the blood vessels, vacuolation of hepatic cells, proliferation of connective tissue and hepatic necrosis. Leucocyte aggregation-mostly lymphatic in nature-was seen infiltrating hepatic tissue. These alterations became more pronounced in liver of fishes exposed to second concentrations indicating more progressive signs of necrosis. The presence of eosinophilic oedematous areas surrounding some blood vessels was also observed. Finally, at the third concentration, in addition to the above alterations, melanomacrophages, which store lipofuscin at the site of necrosis, were observed. These histological results imply that the fish liver may serve as a target organ for the toxicity of sublethal concentrations of lead nitrate.

Histopathological biomarkers in juvenile silver catfish (Rhamdia quelen) exposed to a sublethal lead concentration

“…Despite the role of liver in heavy metal detoxification (Heath, 1995), few studies have described the effects of acute Pb toxicity on liver histopathology in fish. As was observed in R. quelen, Suiçmez et al (2006) reported venous congestion and hepatocytes necrosis in Oncorhynchus mykiss (Walbaum) exposed to 10 mg l À 1 Pb for 72-h. After 7 days of exposure to the same concentration, Khdir et al (2012) only observed an increase of hepatocyte vacuolization in O. niloticus.…”

Effects of Two Sublethal Concentrations of Mercury Chloride on the Morphology and Metallothionein Activity in the Liver of Zebrafish (Danio rerio)

“…Glycogen depletion has been reported in liver fishes, after short and long term exposure to other heavy metals, such as copper, cadmium and lead [ 48 , 50 , 51 ]. Moreover, similar glycogen perturbations have also been recorded in both liver and muscle of Oreochromis mossambicus as result of mercury chloride toxicity; Roy George and colleagues [ 27 ] suggested that the great loss of glycogen in the liver indicates that it is the most affected organ during stress.…”

Morphological and Functional Alterations in Zebrafish (Danio rerio) Liver after Exposure to Two Ecologically Relevant Concentrations of Lead

“…According to the previous reports on Oreochromis niloticus when chronically exposed to high Pb concentrations [33,61], the first and most frequent alteration observed in D. rerio liver was the congestion of blood vessels and sinusoids. Such circulatory alterations have been regarded as reversible modifications that do not alter the normal function of the tissue [59], leading us to suppose that a recovery of the health status would be possible if the input of the toxicant ceased.…”