LIQUID-CHROMATOGRAPHIC MASS-SPECTROMETRIC STUDIES ON THE ENZYMATIC DEGRADATION OF GONADOTROPIN-RELEASING-HORMONE

Gonadotropin-releasing hormone (GnRH) derivatives are used in cancer t herapy, but relatively little is known about their metabolic fate in t he organism. This paper describes the application of high-performance liquid chromatography combined with electrospray mass spectrometry to identify the degradation products resulting from the incubation of two GnRH analogues, D-Phe(6)-GnRH and DSer(OtBu)(6)-desGly(10)-GnRH-ethyl amide (buserelin) with rat kidney membranes. Reversed-phase columns we re applied with gradient elution using a flow-rate of ca. 2 mu l/min t o the mass spectrometer. Post- and precolumn stream splitting were emp loyed to adjust the flow-rates for columns of 2 and 0.32 mm I.D. The p attern of peptide degradation products obtained with this method indic ates that a defined proteolytic membrane enzyme system is responsible for these catabolic processes.