DEVELOPMENTAL AND AGING CHANGES IN AMINOPEPTIDASE ACTIVITIES IN SELECTED TISSUES OF THE RAT

Aminopeptidase activities, assayed as arylamidase activities, were inv estigated in selected tissues of 1, 6, 12 and 24-month-old rats. The e nzyme activities were found to have a heterogeneous distribution and a ge-related changes were observed. The highest levels of soluble arginy l-aminopeptidase activity were detected in brain homogenate at all the studied ages, whereas membrane-bound activity presented the highest l evels in brain and kidney in the four ages tested. Aspartyl-aminopepti dase activity was detected mainly in the particulate fraction of kidne y at all four ages. In 1, 6 and 12-month-old animals, soluble aspartyl -aminopeptidase activity was also higher in the kidney than in the res t of the tissues, whereas in the group of 2-year-old rats, the highest levels were found in both kidney and liver. Age-related changes were observed in all the studied tissues and for all the assayed enzymatic activities. In general, the maximal levels were detected in both the y oungest and the oldest animals, and the minimal ones in 6 and 12-month -old rats. However, in the adrenals, the soluble and membrane-bound ar ginyl-aminopeptidase activity was higher in 6-month and 2-year-old rat s than in 1-month and 12-month-old rats. These changes may reflect the functional status of the susceptible endogenous substrates of aminope ptidases.