A Sensitive Coupled Hplc/ria Technique for Separation of Endorphins : Multiple Forms of B-endorphin in Rat Pituitary Intermediate vs. Anterior Lobe

A technique is described which couples High Performance Liquid Chromatography (HPLC) to radioimmuno assays (RIA) , thus achieving high sensitivity with good specificity. This method allows the separation and detection of multiple forms of immunoreactive peptides. Using this procedure, we have characterized the B-E-like immunoreactivity in rat pituitary. It had been previously reported that most of the B-E-sized material in both intermediate and anterior lobe of rat pituitary is not true B-El_31. We now report that N-acetyl B-El-27, which is inactive at the opiate receptor, is indeed the predominant peptide in rat intermediate lobe, with B-El-31 representing a low proportion of the immunoreactivity. On the other hand, the opiate active B-ENDl_31 is the predominant peptide in the anterior lobe. These findings have important implications for the physiological and behavioral roles of the pituitary opioids.