The pentapeptide thymopentin (Arg-Lys-Asp-Val-Tyr, RKDVY) corresponds to amino acids 32-36 of the 49 amino acid immunomodulatory polypeptide, thymopoietin, whose biological activity is partially reproduced. Thymopentin is widely used in the clinic and represents a promising target for drug design but bioanalytical and pharmacokinetic data are limited due to its enzymatic instability. This paper reports a rapid and sensitive method based on liquid chromatography with tandem mass spectrometry for the determination of thymopentin in beagle dog blood. To inactivate peptidases and stabilize thymopentin, acetonitrile was added to blood samples immediately after collection followed by addition of stable isotope-labeled thymopentin as internal standard and washing with dichloromethane. Chromatography was carried out on an Ascentis Express Peptide ES-C-18 column using gradient elution with methanol and aqueous 0.1% formic acid at a flow rate of 0.6 mL/min. Positive electrospray ionization mass spectrometry with selected reaction monitoring achieved linearity in the range of 1.5-800 ng/mL with good accuracy/precision and minimal matrix effects. The method was successfully applied to a pharmacokinetic study in beagle dogs after intravenous administration of 0.2 mg/kg thymopentin.
[1]Jilin Univ, Coll Life Sci, Changchun 130012, Peoples R China.
[2]Jilin Univ, Sch Pharmaceut Sci, Changchun 130012, Peoples R China.
[3]Queens Univ, Dept Med, Div Rheumatol, Kingston, ON K7L 3N6, Canada.
[4]Jilin Univ, Res Ctr Drug Metab, Changchun 130012, Peoples R China.
[5]Jilin Univ, Hosp 1, Res Inst Translat Med, Clin Pharmacol Ctr, Changchun 130012, Peoples R China.
[6]Univ Otago, Sch Pharm, Dunedin, New Zealand.
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