Adrenomedullary catecholaminergic activity increases with age in male laboratory rodents

In this report, we have examined the effects of aging on adrenomedullary catecholaminergic activity by evaluating the levels of activity of adrenal dopamine-beta-hydroxylase (DBH) in three species of laboratory rodents. Groups of male Fischer 344 rats (3-, 18-, and 28-month-old), Chinese hamsters (4- and 30-month-old), and Mongolian gerbils (3- and 26-month-old) were killed, and their adrenal DBH activities were measured by a sensitive radioenzymatic method. The results indicated that adrenomedullary DBH activities showed a progressive age-related increase in all three species investigated. Specifically, (a) adrenal DBH activity in the 18-month-old rats was significantly (p less than .001) higher than that of 3-month-old rats, and the enzyme activity in the 28-month-old rats was significantly (p less than .001) higher than that of the 18-month-old rats; (b) adrenal DBH activity in the 30-month-old hamsters showed a significant (p less than .001) increase over that found in the 4-month-old hamsters; and (c) DBH activity in the 26-month-old gerbils was significantly (p less than .05) higher than that noted in 3-month-old gerbils. These results suggest that an age-related increase in adrenal DBH activity may, at least in part, contribute to increased levels of circulating catecholamines.