CHARACTERIZATION OF GENTAMICIN-INDUCED DYSFUNCTIONS IN-VITRO - THE USE OF OPTIMIZED PRIMARY CULTURES OF RABBIT PROXIMAL TUBULE CELLS

Compared to prior studies which frequently pinpoint the impairment of one parameter or function, this paper reports for the first time an ex tensive characterization of the toxic effects of gentamicin in a singl e model of primary cultured rabbit proximal tubule cells developed wit hout insulin and glucose. Biochemical, functional and morphological ap proaches were used. Cellular response pattern was examined after a 72- h exposure during either the exponential growth phase or the stationar y confluency phase of the culture to 0.2, 1, and 2.5 mM gentamicin. Th e biochemical study after gentamicin exposure showed increased activit ies for N-acetyl-beta-D-glucosaminidase and alkaline phosphatase, decr eased activities for sphingomyelinase, cathepsin B, Na+/K+-ATPase, lac tate dehydrogenase and NADPH cytochrome C reductase. Functional evalua tion revealed decreased protein synthesis and alpha-methylglucose tran sport after gentamicin exposure. Morphometric study made it possible t o show that the density of lysosomes, the cell fractional volume of th e lysosomal compartment, and the mean size of the lysosomal profiles a re increased in the cells. Intracellular accumulation of gentamicin in proximal tubular cells was dose dependent and reached high levels in cultured cells. In conclusion, this model compared to others in the li terature allowed us to demonstrate in vitro a close response pattern t o the in vivo situation after gentamicin exposure.