Chromatographic characterization of dynorphin and [Leu 5]enkephalin immunoreactivity in guinea pig and rat testis

Abstract

Tissues of the reproductive tract have been shown to contain mRNAs coding for pro-opiomelanocortin (POMC), pro-enkephalin and pro-dynorphin. However, the amounts of immunoreactive opioid peptides in these tissues are low, and in the case of the enkephalins and dynorphin, the molecular species responsible for the immunoreactivities have not been characterized. The chromatographic properties of dynorphin and enkephalin immunoreactivities in extracts of guinea pig and rat testis have therefore been determined. Dynorphin A and dynorphin B immunoreactivity was heterogeneous, with a significant amount attributable to high-molecular-weight forms. About 20% of the dynorphin A immunoreactivity, and about 40% of the dynorphin B immunoreactivity, in guinea pig testis extracts behaved as authentic dynorphin A or B, respectively during fractionation by ion exchange, gel filtration and high-performance liquid chromatography. Both high- and low-molecular-weight forms of [Leu 5]enkephalin immunoreactivity were also present, with roughly 50–70% of the immunoreactivity attributable to low-molecular-weight forms. In extracts of guinea pig testis only a small part of this immunoreactivity eluted as authentic [Leu 5]enkephalin during high-performance liquid chromatrography. In rat testis most of the low-molecular-weight [Leu 5]enkephalin immunoreactivity behaved as the authentic peptide. These results confirm that opioid peptides are produced in guinea pig and rat testis, and demonstrate that immunoreactive forms of the peptides similar to those found in brain and pituitary are present in the tissue.