title: Nonlinear pharmacokinetics of L-N(G)-methyl-arginine in rats: characterization by an improved HPLC assay.
abstract: L-N(G)-methyl-arginine (L-NMMA) is an inhibitor of nitric oxide synthase (NOS) enzymes. We have characterized the pharmacokinetics of L-NMMA in rats using HPLC. The HPLC assay requires pre-column derivatization, gradient elution and ultraviolet detection. The limit of sensitivity in plasma was 3.0 microM (0.75 microg mL(-1)). Using this assay, the pharmacokinetics of L-NMMA were characterized following iv bolus doses of 25, 50 and 100 mg kg(-1). Compartmental and noncompartmental data analysis suggest that L-NMMA pharmacokinetics are nonlinear at these doses. From the nonlinear compartmental analysis, we estimated the K(m) and V(max) parameters of L-NMMA elimination to be 70.2 microM and 4.59 microM min(-1), respectively. This estimated K(m) value of L-NMMA elimination is consistent with its nonlinear elimination characteristics in humans and its saturable metabolism by the N(G), N(G)-dimethylarginine dimethylamino-hydrolase enzyme in isolated rat tissue.
authors.affiliation: Department of Pharmaceutics, School of Pharmacy, State University of New York at Buffalo, Buffalo, NY 14260-1200, USA.
authors.forename: T S
authors.initials: TS
authors.lastname: Maurer
authors.forename: Y
authors.initials: Y
authors.lastname: Mishra
authors.forename: H L
authors.initials: HL
authors.lastname: Fung
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics*; D008297:Male; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019323:omega-N-Methylarginine / Q000493:pharmacokinetics*
chemical_list: D004791:Enzyme Inhibitors; D019323:omega-N-Methylarginine; D019001:Nitric Oxide Synthase