CONICET | Buscador de Institutos y Recursos Humanos

Metallothioneins (MTs) are characteristic proteins involved in the homeostasis and detoxification processes of essential and non-essential metals, being these contaminants able to induce their synthesis. Although MTs were reported in several mammalian tissues, studies in marine mammal blood are very scarce. The study was performed in blood samples of fourteen South American sea lion females (nine juveniles and five adults) from Isla de Lobos (35º0138S-54º5255W, Uruguay). The sea lions were physically restrained and sedated with inhalatory anesthesia (isofluorane). Blood samples were taken from the hind flippers; blood cells and plasma were separated by centrifugation and immediately frozen in liquid nitrogen and conserved at laboratory under -80ºC. MTs were determined by Differential Pulse Polarography by Static Drop Mercury Electrode; using a solution of [Co(NH3)6]Cl, NH4Cl and NH4OH as electrolytical support andTriton X-100 to minimize cobalt peak. A MT standard (MT-1 liver rabbit, Sigma) was used for identification and quantification of proteins. Relatively high MT levels were found in both fractions of blood (cells and plasma) of both juveniles and adults, compared to other groups (fish and invertebrates) and hepatic values reported for other Pinnipeds. These results could be associated to the high metal levels usually found in liver and kidney of marine mammals, particularly in O. flavescens. Similar MT levels were found in blood cells and plasma, suggesting a low differential partition between fractions. These results can be justified by the fact that blood is considered a metal transporting tissue more than an accumulator one, although it was proposed that metals from blood are slowly released and have a long average life. The results obtained in O. flavescens indicate that MT in blood could be a good biomarker of individual sensitivity to metallic stress in Pinnipeds.

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