Age-related changes in catalase activity and its inhibition by manganese (II) chloride in the brain of two species of poikilothermic vertebrates

Two species of poikilothermic vertebrates, a teleost fish (Channa punctatus) and the garden lizard (Calotes versicolor) were used to study the effect of age on brain catalase (CT) activity and its inhibition by manganese (II) chloride (MnCl2). While in fish the CT activity of brain remained unchanged throughout the lifespan, the enzyme activity decreased during maturation and then showed an increase during aging in the garden lizard. MnCl2 at a concentration of 333 μM in incubating medium significantly inhibited the CT activity of the brain of both fishes and lizards of all the three age groups (young, middle-aged and old), the degree of inhibition showing a trend of increase with advancing age. However, statistical significance was observed when fishes of the young age group were compared either with those of middle-aged or old counterparts, and between young versus old and middle-aged versus old lizards. Increased susceptibility to Mn2+ during aging suggests changes in regulation of CT.