SUMMARY
The qualitative analyse of Bohr effect by isoelectric focusing on polyacrilamide gel from hemolysed of the seven species hemoglobins of Loricariidae and Callicthidae family of Amazon River have a heterogeneous effect. Some of them have shown hemoglobins with isoelectric point which increase when the protein is in deoxygenated state in comparison to the carboxy state, likely human hemoglobin. Others presented its hemoglobins in the deoxy state without any change in the PI or have presented an decrease in such as value. The changes in isoelectric point when the carboxyhemoglobin was comproved with the deoxyhemoglobin have been used as Bohr effect's indicator. Thus, Pterygoplychthis pardalis presents a reverse Bohr effect that was confirmed by oxygen equilibrium analysis. Plecostomus; Canthoporus and Hoplosternum throcatum showed hemoglobins with normal Bohr effect. On the other hand Sturisoma robustum presented one hemoglobin component with normal and others with reverse Bohr effects. A close relationship between Bohr effect analysed by this methodology and that usually done by equilibrium studies could be observed. The heterogeneous Bohr effect could be correlated with the habitat or their ability to survive in hypoxic environment.