Quantification of ß-aminopropionitrile, an inhibitor of lysyl oxidase activity, in plasma and tumor of mice by liquid chromatography tandem mass spectrometry.

Lysyl oxidase enzymes are reported to be involved in patho-physiological process such as tumorigenesis. ß-Aminopropionitrile (BAPN) is an irreversible inhibitor of lysyl oxidase activity, suggesting a potentially useful therapeutic of interest in oncology. This paper describes the first assay concerning the quantification of BAPN by mass spectrometry. A high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS) assay was developed for the quantification of BAPN in plasma and tumor of mice. This method combines dansyl chloride (Dns) derivatization and extraction using a solid-phase extraction Oasis Max column. Deuterated BAPN was used as internal standard (IS). Separation was achieved using an C18 column HypersylGold, (ThermoElectron), 3.0 µm (100 × 2.1 mm i.d.). Gradient elution with water containing 0.1% acetic acid (A) and acetonitrile containing 0.1% acetic acid (B) was applied. Detection was performed with an electrospray ionization interface operating in negative ion mode. Selected reaction monitoring was used with ion transitions m/z 302 → 249 for BAPN-Dns and m/z 306 → 250 for the IS. The method was fully validated in plasma and was linear and sensitive in the range of 10-500 ng/mL. The lower limit of quantification in plasma was 2.5 ng/mL. This validated assay was successfully applied to a kinetic study of BAPN in mouse plasma and demonstrates that BAPN reaches the tumoral tissue.

Urinary excretion of beta-aminopropionitrile and cyanoacetic acid.

Human serum did not convert beta-aminopropionitrile (BAPN) to the deaminated, nonlathyrogenic metabolite, cyanoacetic acid (CAA). Instead, its enzymic activity for oxidizing benzylamine was inhibited by BAPN (I50 = 2 X 10(-3) M). BAPN was found in the urine within one hour of oral administration. Oral 250 mg BAPN at 6-hr intervals each day for 21 days resulted in urinary BAPN recoveries approximating 16% of the total dose. BAPN was not detected in urine in specimens collected later than 7 hr after cessation of BAPN dosage. Urinary CAA appeared more slowly than BAPN and increased gradually to approximately three times that of urinary BAPN. After BAPN was discontinued, there was prolonged urinary excretion of BAPN-derived CAA. These along with earlier findings in experimental animals suggest that unexcreted BAPN is sequestered in tissues where it is metabolized to CAA before slowly released.

Pharmacokinetic analysis of beta-aminopropionitrile in rabbits.

beta-Aminopropionitrile (beta APN), inhibits the activity of lysyl oxidase, an important enzyme for the post-translational formation of inter- and intramolecular covalent cross-linking between the connective tissue proteins, collagen and elastin. We became interested in the possible use of this compound as a therapeutic agent in the so-called human collagen diseases. beta APN's action mechanism is known, but its pharmacokinetics in rabbits have not yet been determined. The present study defined the kinetic parameters of beta APN in rabbits, after oral or intravenous (iv) administration. The HPLC technique was recently modified using OPA (ortho-phthalaldehyde) as the derivative agent. beta APN plasma concentration vs time following the iv administration of 200 mg/kg was best described by the biexponential equation C = 92.43.e(-0.0728 t) + 61.78.e(-0.0088 t) (t1/2 beta = 78.73 +/- 5.19 min; Vc = 1.29 +/- 0.04 L.kg-1). After oral administration, beta APN followed a zero-order absorption pattern (Ko = 3.02 +/- 0.34 mg.kg-1.min-1), which means that the beta APN reached the blood very quickly.