A suspension of renal tubule fragments from the rat was prepared by a method involving collagenase digestion of the excised renal cortex and dispersion of the digest by passage through a nylon mesh. Through the use of scanning electronmicroscopy it was confirmed that the tubular lumena were patent, thus ensuring access of medium to both the luminal and the contraluminal membranes of the tubular cells. The viability of the tubule fragments was ascertained by measuring the rate of formation of glucose from pyruvate as substrate and the uptake of [14C] L-lysine against a concentration gradient. The uptake of L-lysine was unimpaired in the presence of gentamicin (10(-3) M), suggesting that there is no competition between this basic amino acid and the polycationic aminoglycoside for transport into tubular cells. The uptake of [3H] gentamicin was studied and found to be reduced in the presence of 2,4-dinitrophenol, potassium cyanide, and ouabain. The reduced uptake in the presence of ouabain was interpreted to mean that a component of gentamicin uptake, which occurs at the luminal membrane, may be driven by the Na+ gradient created by Na+-K+ATPase activity at the contraluminal membrane. This renal tubule preparation offers advantages over the kidney-slice technique for studies into the mechanisms of aminoglycoside nephrotoxicity.
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