Histopathological analysis of the olfactory epithelium of zebrafish (Danio rerio) exposed to sublethal doses of urea.
Chronic renal disease is known to alter olfactory function, but the specific changes induced in olfactory organs during this process remain unclear. Of the uraemic toxins generated during renal disease, high levels of urea are known to induce hyposmic conditions. In this study, the effects of environmental exposure to elevated concentrations of urea (7, 13.5 and 20 g L(-1)) on the sensory mucosa of zebrafish in acute toxicity and chronic toxicity tests were described. It was observed that lamellae maintained structural integrity and epithelial thickness was slightly reduced, but only following exposure to the highest concentrations of urea. Pan-neuronal labelling with anti-Hu revealed a negative correlation with levels of urea, leading to investigation of whether distinct neuronal subtypes were equally sensitive. Using densitometric analysis of immunolabelled tissues, numbers of Gα olf-, TRPC2- and TrkA-expressing cells were compared, representing ciliated, microvillous and crypt neurons, respectively. The three neuronal subpopulations responded differently to increasing levels of urea. In particular, crypt cells were more severely affected than the other cell types, and Gα olf-immunoreactivity was found to increase when fish were exposed to low doses of urea. It can be concluded that exposure to moderate levels of urea leads to sensory toxicity directly affecting olfactory organs, in accordance with the functional olfactometric measurements previously reported in the literature.
Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
Simone
S
Bettini
Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
Maurizio
M
Lazzari
Department of Earth, Environmental and Life Science, University of Genoa, Genoa, Italy.
Sara
S
Ferrando
Department of Earth, Environmental and Life Science, University of Genoa, Genoa, Italy.
Lorenzo
L
Gallus
Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
Valeria
V
Franceschini
D000704:Analysis of Variance; D000818:Animals; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism; D007150:Immunohistochemistry; D009830:Olfactory Bulb / Q000187:drug effects; D009831:Olfactory Mucosa / Q000187:drug effects*; D018034:Olfactory Receptor Neurons / Q000187:drug effects; D014508:Urea / Q000633:toxicity*; D014873:Water Pollutants / Q000633:toxicity*; D015027:Zebrafish / Q000502:physiology*
D044385:GTP-Binding Protein alpha Subunits; D014873:Water Pollutants; C084618:olfactory G protein subunit alpha olf; D014508:Urea
Gα olf; PCNA; TRPC2; TrkA; neuroepithelium