Uptake and intracellular distribution of 4,4′-diacetyldiphenylurea-bis-(guanylhydrazone) in sensitive and resistant leukemia L1210 cells

Abstract

The uptake and intracellular distribution of 4, 4′-diacetyldiphenylurea-bis(guanylhydrazone) has been studied in vitro and in vivo using cells from leukemia L1210 and a subline resistant to the drug. The uptake process involved a very rapid adsorption, presumably to the cell exterior, followed by actual cellular uptake and firm binding of the drug to the cell. Both adsorption and binding occurred concurrently, although within the first few minutes adsorption predominated. The uptake exhibited first-order kinetics over a 10,000-fold range of external drug concentration with a k 37 of about 0·5 min −1 and a Q 10 of about 2·0. The intracellular-free drug concentration was found to be nearly equal to the extracellular drug concentration. Uptake was not decreased in the presence of sodium para-chloromercuribenzoate, 2, 4-dinitrophenol, of 4, 4'-diacetyldiphenylurea-mono(guanylhydrazone), or when cells were incubated in Ringer solution without calcium and glucose or killed by X-radiation. These findings support the conclusion that 4,4'-diacetyldiphenylurea-bis(guanylhydrazone) is taken up by passive diffusion. In resistant L1210 cells, the different parameters of uptake studied were uniformly 30–50 per cent lower than those found in sensitive L1210 cells; also in this case the intracellular-free drug concentration was nearly the same as the extracellular concentration. A large proportion of the drug taken up was bound to mitochondrial and nuclear fractions. The cellular uptake appeared to be rate-limited by binding or uptake within cellular compartments. The reduced rate of uptake in resistant L1210 was consistent with resistance and appeared to be related to alterations in the binding capacity of cellular organelles.