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

Abstract

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 it is clear if the rate or pathways of degradation are changed during chronic stress. To explore these issues, we incubated [3H][beta]-endorphinh 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.