Degradation of [3H]beta-endorphin in rat plasma is increased with chronic stress

With a number of acute stressors beta-endorphin is released into plasma. It is unclear if beta-endorphin is converted into any other biologically active products, nor is it clear if the rate or pathways of degradation are changed during chronic stress. To explore these issues, we incubated [3H]beta-endorphin h labeled in positions 1 and 27 with plasma from normal and chronically footshocked rats and measured the rate of conversion of the label from beta-endorphin size material to smaller size material. Initial separations were done using a G-50 molecular sieving column, with subsequent characterization and identification on HPLC. By G-50 sieving, there is a time dependent formation of only one radioactive peak. HPLC identification demonstrates gamma-endorphin and another unidentified peak. This enzymatic activity is increased in the plasma of chronically stressed rats.