Evaluation of Dermorphin Metabolism Using Zebrafish Water Tank Model and Human Liver Microsomes

Background: Dermorphin is a heptapeptide with an analgesic potential higher than morphine that does not present the same risk for the development of tolerance. These pharmacological features make dermorphin a potential doping agent in competitive sports and it is already prohibited for racehorses. For athletes, the development of an efficient strategy to monitor for its abuse necessitates an investigation of the metabolism of dermorphin in humans. Methods: Here, human liver microsomes and zebrafish were utilized as model systems of human metabolism to evaluate the presence and kinetics of metabolites derived from dermorphin. Five hours after its administration, the presence of dermorphin metabolites could be detected in both models by liquid chromatography coupled to highresolution mass spectrometry. Results: Although the two models showed common results, marked differences were also observed in relation to the formed metabolites. Six putative metabolites, based on their exact masses of m/z 479.1915, m/z 501.1733, m/z 495.1657, m/z 223.1073, m/z 180.1017 and m/z 457.2085, are proposed to represent the metabolic pattern of dermorphin. The major metabolite generated from the administration of dermorphin in both models was YAFG-OH (m/z 457.2085), which is the N-terminal tetrapeptide previously identified from studies on rats. Conclusion: Its extensive characterization and commercial availability suggest that it could serve as a primary target analyte for the detection of dermorphin misuse. The metabolomics approach also allowed the assignment of other confirmatory metabolites. morphin acts as an agonist to the same opioid receptors as morphine, but with greater efficiency that could result in a lower probability of causing tolerance [2, 3-6]. Rat animal models have been used in the majority of experiments aimed at a determination of the pharmacokinetics and pharmacodynamics of this peptide [6-8]. The main dermorphin metabolite generated was the N-terminal tetrapeptide of dermorphin (YAFG) [8] and 86% of the dermorphin administered to rats appeared to be biotransformed in the liver [7]. Addi