Carbaryl tricompartmental toxicokinetics and anticholinesterase activity

The blood kinetics of carbaryl and the inhibition of plasma acetylcholinesterases were followed for 24 h after administration of 20 mg/kg [14C]carbaryl (0.17 microCi/mg). The kinetics of the radioactivity attributed to unaltered carbaryl is bi-exponential whereas that of the total 14C activity is tri-exponential. The kinetics were treated with open 2- and 3-compartment models respectively. The exchange rate constants between the various compartments as well as the elimination constant (expressed in h-1) were found to be: k12 = 1.93, k21 = 1.18 and k10 = 2.46 (2-compartment model) and k'12 = 18.65, k'21 = 13.90, k'13 = 1.14 k'31 = 0.125 and k'10 = 0.672 (3-compartment model). The 3-compartment model demonstrates the persistence in the blood of 14C activity which correlated with plasma acetylcholinesterase inhibition.