Sensitive method for measuring hydrolysis of enkephalins in plasma, using high-performance liquid chromatography with electrochemical detection.

This paper describes a simple and sensitive method for detection of [Leu]- and [Met]enkephalin and their N-terminal tyrosine-containing metabolic fragments (Tyr, Tyr-Gly, Tyr-Gly-Gly, and Tyr-Gly-Gly-Phe), using high-performance liquid chromatography with electrochemical detection. The method employs a carbon graphite working electrode with increased working electrode surface area (40 mm2). The procedures were applied to assay of the activities of enkephalin-degrading enzymes in whole plasma collected from rats, mice, and chicks.