Lactate dehydrogenase, succinate dehydrogenase and nucleotide tetrazolium reductase histochemical activities in the mesentric arteries and arterioles of young and old rats.

Age-related changes of the metabolic characteristics of large, medium and small brances of the rat superior mesenteric artery were investigated in young (4 month) and old (25 month) male Wistar rats, using enzyme histochemical techniques. The following enzymatic activities were examined: lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH); NADPH(2)-tetrazolium reductase (NADPHD) and NADH(2)-tetrazolium reductase (NADHD). The intensity of enzymatic reactions within the tunica media of the large, medium and small branches and within the tunica intima of the large and medium branches of the artery was assessed microphotometrically. In young rats the reactivity of enzymes investigated is similar in both the tunica media and the intima with the exception of SDH which reacts stronger in the media than in the intima. LDH and NADHD displayed the most intense reaction whereas SDH reaction was less intense. In old rats LDH and NADPHD reactivity decreased, SDH reactivity increased in the intima of large and medium branches; and SDH increased in the media of large branches. The possibility is discussed that an impaired endothelial function may represent one of the most consistent phenomena of aging of the superior mesenteric artery.