Erythromycin toxicity in primary cultures of rat hepatocytes

1. 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).

2. EF was not cytotoxic after 18 h incubation at concentrations up to 8 × 10^?4 M and EE was much more toxic than EB at all concentrations studied.

3. EE toxicity was greater in a serum-free medium and was not increased by induction of cytochrome P-450 with phenobarbitone.

4. 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.

5. 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.