Streptomycin toxicity in primary cultures of flounder renal proximal tubule cells

Summary The aminoglycoside antibiotic streptomycin is a known nephrotoxin in vivo and a common component of cell culture media. The effects of streptomycin (100 μg/ml) on transepithelial electrical properties, glucose transport, glycolytic metabolism, and morphology were examined in primary proximal tubule cell cultures from winter flounder (Pseudopleuronectes americanus) kidney. Streptomycin treatment on either Days 2 to 12 or Days 8 to 13 abolished the transepithelial potential difference and short-circuit current across the monolayer but had no effect on transepithelial resistance in confluent 12 to 13-dcultures, suggesting the loss of active transepithelial transport. Consistent with these findings, mucosal-to-serosal glucose fluxes were greatly reduced in streptomycin-treated cultures and insensitive to the transport inhibitor phlorizin, indicating the absence of the apical Na-dependent glucose transport system associated with net glucose reabsorption. In addition to transport processes, antibiotic treatment also interfered with cellular energy metabolism as judged by the rapid reduction in glycolytic lactate production observed in the presence of streptomycin. Scanning and transmission electron microscopy revealed that streptomycin-treated culture were composed of cuboidal-to-columnar shaped cells which maintained intact tight junctions similar to control cultures. However, apical microvilli, the presumed sites of mucosal transport systems, were severely reduced in number in streptomycin-treated cultures. We concluded that streptomycin, at a dose commonly used in cell culture, inhibited the expression of differentiated function by flounder proximal tubule cell cultures. These cell cultures may provide a suitable model system for examination of the mechanisms of aminoglycoside nephrotoxicity. This investigation was supported by the University of Connecticut Research Foundation and by grant PCM-8003452 from the National Science Foundation, Washington, DC.