Erythromycin toxicity in primary cultures of rat hepatocytes

Cultured rat hepatocytes were used to study the toxicity of erythromycin base (EB), erythromycin estolate (EE) and a new fluorinated derivative, (8S)-8-fluoroerythromycin A (EF). EF was not cytotoxic after 18 h incubation at concentrations up to 8 X 10(-4) M and EE was much more toxic than EB at all concentrations studied. EE toxicity was greater in a serum-free medium and was not increased by induction of cytochrome P-450 with phenobarbitone. In hepatocytes co-cultured with rat-liver epithelial cells EE, but not EF, raised the cytochrome P-450 content and formed stable cytochrome P-450 complexes with about 40% of the haemoprotein. The lack of correlation between cytochrome P-450 content and cytotoxicity suggests that some of the parent erythromycin drugs and not their metabolites are the toxic entities.