[Subcellular distribution of soluble and membrane-bound aminopeptidase in the left and right hemispheres of young and adult rats].

The levels of soluble and membrane-bound aminopeptidase activities were assayed in subcellular fractions from young (1 month old) and adult (5 month old) left and right rat brains, using Leu-, Arg- and Asp-2-naphthylamide as substrates. Both soluble Leu- and Arg-aminopeptidase activities showed the highest levels in the synaptosomal fraction in the two groups of rats. The highest levels of membrane-bound Leu- and Arg-aminopeptidase activities were found in the microsomal fraction of the two ages studied. There were no differences between the two ages in soluble Leu- and Arg- aminopeptidase activities. However, a significant decrease in both membrane-bound activities was evidenced in the synaptosomal fraction of adult rats. The young rats showed the highest soluble and membrane-bound levels of Asp-aminopeptidase activity in the microsomal fraction but no differences among fractions were found at 5 months of age. The soluble Asp-aminopeptidase activity of the homogenate and the mitochondrial fraction was significantly increased in adult animals when compared to that of younger ones. Finally, no differences between left and right brains, in soluble or membrane-bound activities, were found neither in young animals nor in the adult ones.