Cyanobacteria has been used as antioxidant in some toxicological models, as well as fluorescent markers and, but little is known about its role in oxidative stress protection. To analyze the effect of phycocianin (PC) on J774A.1 cell cultures, were exposed to an oxidative media generated by ascorbic acid in the presence of Cu(II), and in a control culture without exposure to ROS. After a period of incubation cell viability was obtained and total protein content was measured by Bradford assay; the electrophoretic pattern was obtained by SDS‐PAGE. Results showed that there are differences in the viability and these correlate to the total protein content found under oxidative stress conditions and different PC concentrations. Electrophoretic patterns suggest that the expression of some proteins depend upon the PC concentration added to the oxidative media; this result is related to the content of total protein. Supported by COFAA and EDD, IPN.