Pharmacokinetics of thrombin-like enzyme from venom of Agkistrodon halys ussuriensis Emelianov determined by ELISA in the rat

Abstract

A thrombin-like enzyme (TLE) was separated and purified from the venom of a northeast Chinese snake Agkistrodon halys ussuriensis Emelianov. Experiments were performed in rats to determine the pharmacokinetic parameters following an intravenous (i.v.) or a subcutaneous (s.c.) injection of the thrombin-like enzyme. The plasma levels of TLE were estimated by enzyme-linked immunosorbent assay. The method exhibited high reproducibility and accuracy in correlating optical densities with TLE concentrations (0.2–30 ng ml −1, r=0.99). The plasma concentration-time course after i.v. administration of 50 μg kg −1 TLE was well fitted by a two-compartment open model. The half-life of the α-phase was 18.0±3.2 min, and that of the β-phase 3.9±0.7 h. The apparent volume of distribution was 1.8±0.5 l kg −1, and clearance was 5.4±0.5 ml min −1 kg −1. When the TLE was injected s.c. at a dose of 0.75 mg kg −1, the changes in plasma concentration were best described by a two-compartment model with a first-order absorption. The maximal plasma level of 51±2.7 ng ml −1 was reached at 5.2±0.5 h. The absorption rate constant was 0.3±0.03 h −1. The area under the plasma concentration-time curve (AUC) was 2.8±0.8 μg h −1 ml −1.