In vitro assessment of trospectomycin and gentamicin sulphate in the LLC-PK(1) cell line

Concurrent use of more than one antibiotic in clinical treatment of serious infections is common. Trospectomycin sulphate, a semi-synthetic aminocyclitol, may be used in combination with the aminoglycoside gentamicin sulphate. To investigate any potential interaction, trospectomycin and gentamicin toxicity were assessed in vitro using a two-factor response surface design study with each factor at four levels. Cultures of the LLC-PK(1) cell line (proximal renal epithelium) were treated with 0, 125, 250 or 500 mug/ml of the drugs, alone or in combination, and cytotoxicity was evaluated at 3, 7, 10 and 14 days of continuous exposure. Cytotoxicity was assessed by morphological and biochemical criteria (lactate dehydrogenase, LDH; alkaline phosphatase, ALP; gamma-glutamyl transpeptidase, GGT; aspartate transaminase, AST; alanine transaminase, ALT; acid phosphatase, ACP). ALP, GGT, LDH and AST activity increased in the control cultures over the experimental period. Cytoplasmic vacuolation, increased number of detached cells and reduced dome formation occurred at 250 and 500 mug gentamicin/ml and in combination with these levels of trospectomycin at study days 10 and 14. There was a statistically significant (P < 0.05) interaction (decrease) for ALP and GGT at study day 14. In summary, the LLC-PK(1) culture system provides a useful in vitro screen to evaluate potential xenobiotic interactions to assess nephrotoxicity.