First evidence of a leptin-like peptide in a cartilaginous fish.

Leptin is a hormone involved in food intake. Although leptin is evolutionarily conserved, no studies have investigated its presence in cartilaginous fish. Here, we report the presence of leptin-like immunoreactivity in the gastro-intestinal tract and liver of the cartilaginous fish Scyliorhinus canicula using western blot and immunohistochemical analyses. A leptin-like immunoreactive band of 16 kDa was detected in the homogenate of the stomach, whereas no immunoreactivity was observed in the intestine or the liver. Immunohistochemistry of the gastric mucosa revealed leptin-like staining localized to mucous-secreting cells and endocrine cells. This is the first report of a leptin-like peptide in a cartilaginous fish.