Figure 3: Aging is associated with changes in phosphorylation of ERK1/2 and ERK5 proteins in F344XBN rat hearts. Protein isolates of hearts excised from 6-, 27-, 30-, 33- and 36-month rats were analyzed by immunoblotting for changes in total and phosphorylated ERK1/2. A- ERK5. B- Data are mean ┬▒SE (n=6). * indicates significant difference from 6-month group, $ indicates significant difference from 27-month group, # indicates significant difference from 30-month group and @ indicates significant difference from 33-month group (P<0.05).