Dietary protein-induced change in mammalian corticosterone status (index of immune response) during aging

The measurement of corticosterone level in plasma and adrenal glands of male albino rats, maintained with normal diet (20% protein), increased with age from 3 to 18 months without changing its adrenal level. Intake of low protein diet (LPD) (5%) for short-term period of seven consecutive days (STP) increased the plasma and adrenal corticosterone level in 6 month old rats only and decreased only the adrenal corticosterone level in 9, 12 and 18 month old rats. LPD supplementation under long-term period (LTP) of 30 consecutive days increased the plasma corticosterone level with a decrease in its adrenal level in 3 month old rats. In 6 months old, the adrenal corticosterone was increased without affecting its plasma level; whereas in 18 month old rats, the plasma corticosterone level was decreased without affecting adrenal levels under similar conditions. High protein diet (HPD) (40%) consumption under STP conditions decreased the plasma corticosterone level in 3 month old rats and increased the same in 6 month old rats. The adrenal corticosterone level under similar condition was increased in 3 and 18 months old and decreased the same in 9 and 12 month old rats. Supplementation of HPD under LTP significantly decreased the plasma corticosterone in 3 and 9 month old rats, while its increase was observed only in 6 and 18 month old groups. The increase in adrenal corticosterone level was observed under similar conditions (HPD under LTP) in 3 the months old group and decreased the same in the 6 months old group. The present result thus suggest that the adrenocortical response may be modulated with the increase of age, the amount of protein supplemented in the diet and its duration of supplementation.