Coomassie-stained SDS-PAGE (Phastgel gradient 10-15%) of urinary proteins of three different Wistar male rats fed with maintenance diet. Gel replicates of the same rats are shown. The body weights of each animal at bands 1 and 3 first appearance have been highlighted with a square. The mean weight (± SD) of the animals when bands 1 and 3 appeared is also indicated. MW: molecular weight marker. α2u: α2u-globulin standard.