Transmembrane distribution of kanamycin and chloramphenicol: insights into the cytotoxicity of antibacterial drugs

Abstract

Antibiotics are widely used and their abuse has caused ecological hazard. Recently, pollution from pharmaceuticals and personal care products (PPCPs) has aroused great concern among governments and researchers. In order to elucidate the correlations among molecular structure, transmembrane distribution and toxicological effects of different kinds of antibiotics, zebrafish (Danio rerio) embryos and larvae were exposed to two structurally different antibiotics, kanamycin (KAN) and chloramphenicol (CAP). The membrane distribution and toxicological effects of these antibiotics were investigated. The association of KAN with the embryos fitted a general Langmuir isotherm and was attributed to electrostatic attraction and hydrogen bond formation. The saturation number of KAN is 252 ± 13 nmol per embryo and the adsorption constant (5.24 ± 0.05) × 10³ L mol⁻¹. The interaction of CAP with the embryos conformed to a general model of partitioning behavior with the partition coefficient being 14.20 ± 0.94 μL per embryo, and was attributed to hydrophobic effects. More than 89% of the adsorbed KAN was located on the outer surface of the embryonic chorion, but over 80% of the adsorbed CAP entered the internal matrix. High antibiotic concentrations were lethal to most embryos, while low concentrations were teratogenic. KAN and CAP had different transmembrane distribution and their toxicities differed in character. KAN mainly accumulated on the outer membrane caused e.g. axial malformation (AM). In contrast, CAP readily went through the membrane into the cytoplasm and caused e.g. serious pericardial edema (PE), yolk sac edema (YSE) and hemagglutination (HE). The new method could be useful for evaluating the interactions of toxins with membranes and elucidating the mechanisms of cytotoxicity.