Further investigation on aldehyde reductase activity in ageing rat tissues

Abstract

Abstract Aldehyde reductase (AR) activity was measured in whole brain, different brain areas, kidney and duodenum of 23-26 months old rats and then compared to matched animals of 3 months. No significant changes in AR activity were found in whole brain of old rats with D-glucose as substrate. A significant increase in AR activity in old rats was found in striatum (12%), cerebellum (26%), midbrain (6%), brainstem (19%) and hypothalamus (13%) with p-nitrobenzaldehyde, in striatum (14%), midbrain (10%), brainstem (52%), hypothalamus (9%) and hippocampus (20%) with D-glucuronate, in cerebellum (21%) with D-xylose, in striatum (43%), cerebellum (19%) and brainstem (22%) with DL-glyceraldehyde, and in brainstem (15%) with pyridine 3-aldehyde. A significant decrease in AR activity in old rats was found in midbrain (16%), brainstem (19%) and hypothalamus (19%) with D-xylose, and in midbrain (13%) with DL-glyceraldehyde. A significant decrease in AR activity in old rats was found in kidney with p-nitrobenzaldehyde (30%), D-xylose (31%), DL-glyceraldehyde (33%), pyridine 3-aldehyde (27%) and in duodenum with p-nitrobenzaldehyde (21%), but a significant increase was found in duodenum with pyridine 3-aldehyde (29%). Preliminary experiments show an increase (42%) of sorbitol dehydrogenase activity in whole brain of old rats. The present results clearly indicate that the AR activity increase in the brain of old rats is the high-Km form of aldehyde reductase. However, as the activity of the enzyme responsible for the catabolism of sorbitol increases, its accumulation in the brain with age seems to be improbable; this is different from what happens in the eye where enzymatic changes with age appear to favour sorbitol accumulation, which is responsible for cataractogenesis.