Imidocarb depletion from cattle liver and mechanism of retention in isolated bovine hepatocytes

Abstract

Imizol injection (imidocarb) is used for the prevention and treatment of babesiosis in cattle. Studies in sheep indicate that imidocarb is retained in edible tissues (Aliu et al.). In the present study we have set up and validated a high-performance liquid chromatography based method to investigate the retention of imidocarb in cattle liver. Imidocarb was still detectable 224 d after a single therapeutic dose with a half-life of 42.7 d. The mechanism of imidocarb retention by bovine liver was modelled using isolated bovine hepatocytes. Incubations with isolated hepatocytes indicated that [¹⁴C]imidocarb binding was dependent on hepatocyte number and showed signs of saturation. Bound [¹⁴C]imidocarb could be eluted from hepatocytes with buffer and extracted with solvents. Equilibrium dialysis under denaturing conditions (Sun and Dent) indicated that 3% of the [¹⁴C]imidocarb was covalently bound to macromolecules. Although the hepatocyte preparations demonstrated the capacity for phase I and II 7-ethoxycoumarin metabolism no metabolites of [¹⁴C]imidocarb were found. Further in vitro binding studies involving sub-cellular fractionation indicated that [¹⁴C]imidocarb is partitioned largely in the nuclear fraction of bovine liver homogenates and that it binds to deoxyribonucleic acid.