Begleiter A, Lam H P, Goldenberg G J
Cancer Res. 1977 Apr;37(4):1022-7.
The mechanism of uptake of nitrosoureas by L5178Y cells in vitro was investigated. A time course of the uptake of radioactivity on incubation of L5178Y lymphoblast with [14C]-1,3-bis(2-chloroethyl)-1-nitrosourea was linear for 30 min and then entered a plateau phase; it was markedly temperature dependent. A similar time course for cells incubated with [14C]ethylene-labeled 1-(2-chlorethyl)-3-cyclohexyl-1-nitrosourea reached equilibrium rapidly, was temperature independent, and resulted in a relatively low level of uptake of radioactivity. However, cells treated with 3-[cyclohexyl-14C]-1-(2-chlorethyl)-1-nitrosourea had a time course that was linear for 30 min, resulted in much higher levels of uptake of radioactivity, and was strongly temperature dependent. These findings, at least for 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, suggest that some drug decomposition precedes uptake. The percentage of radioactivity found in the cell sap fraction was at least 85% of total cell activity when cells were incubated with any of the three 14C-labeled nitrosoureas. Furthermore, thin-layer chromatography of the cell sap fraction revealed the presence of free intact drug. These findings indicate that intracellular uptake of intact nitrosoureas occurred. A time course of uptake of intact 1,3-bis(2-chloroethyl)-1-nitrosourea reached equilibrium rapidly with cell/medium distribution ratios of 0.2 to 0.6 and was temperature independent. The addition of excess unlabeled 1,3-bis(2-chlorethyl)-1-nitrosourea or 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea had no effect on uptake of [14C]-1,3-bis(2-chloroethyl)-1-nitrosourea, These findings suggest that uptake of intact 1,3-bis(2-chloroethyl)-1-nitrosourea was by passive diffusion. A time course of the uptake of intact 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea with either [14C]ethylene- or ring-labeled drug rapidly reached equilibrium, was temperature independent, and attained a cell/medium ratio greater than unity. Uptake of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea was sodium independent and was unaffected by the metabolic inhibitors (sodium fluoride, sodium cyanide, or 2,4-dinitrophenol) or by urea, a potential physiological competitor. Furthermore, addition of unlabeled 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea or 1,3-bis(2-chlorethyl)-1-nitrosourea had no effect on uptake of labeled 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea. These findings suggest that uptake of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea also occurs by passive diffusion.
研究了L5178Y细胞在体外摄取亚硝基脲的机制。用[¹⁴C]-1,3-双(2-氯乙基)-1-亚硝基脲孵育L5178Y成淋巴细胞时，放射性摄取的时间进程在30分钟内呈线性，然后进入平台期；其明显依赖于温度。用[¹⁴C]乙烯标记的1-(2-氯乙基)-3-环己基-1-亚硝基脲孵育细胞时，类似的时间进程迅速达到平衡，不依赖于温度，且放射性摄取水平相对较低。然而，用3-[环己基-¹⁴C]-1-(2-氯乙基)-1-亚硝基脲处理的细胞，其时间进程在30分钟内呈线性，导致放射性摄取水平高得多，且强烈依赖于温度。这些发现，至少对于1-(2-氯乙基)-3-环己基-1-亚硝基脲而言，表明在摄取之前有一些药物分解。当细胞与三种¹⁴C标记的亚硝基脲中的任何一种孵育时，在细胞液部分发现的放射性百分比至少占细胞总活性的85%。此外，细胞液部分的薄层色谱显示存在游离的完整药物。这些发现表明完整的亚硝基脲发生了细胞内摄取。完整的1,3-双(2-氯乙基)-1-亚硝基脲的摄取时间进程迅速达到平衡，细胞/培养基分布比为0.2至0.6，且不依赖于温度。加入过量未标记的1,3-双(2-氯乙基)-1-亚硝基脲或1-(2-氯乙基)-3-环己基-1-亚硝基脲对[¹⁴C]-1,3-双(2-氯乙基)-1-亚硝基脲的摄取没有影响。这些发现表明完整的1,3-双(2-氯乙基)-1-亚硝基脲的摄取是通过被动扩散进行的。完整的1-(2-氯乙基)-3-环己基-1-亚硝基脲用[¹⁴C]乙烯或环标记药物的摄取时间进程迅速达到平衡，不依赖于温度，且细胞/培养基比大于1。1-(2-氯乙基)-3-环己基-1-亚硝基脲的摄取不依赖于钠，不受代谢抑制剂（氟化钠、氰化钠或2,4-二硝基苯酚）或尿素（一种潜在的生理竞争者）的影响。此外，加入未标记的1-(2-氯乙基)-3-环己基-1-亚硝基脲或1,3-双(2-氯乙基)-1-亚硝基脲对标记的1-(2-氯乙基)-3-环己基-1-亚硝基脲的摄取没有影响。这些发现表明1-(2-氯乙基)-3-环己基-1-亚硝基脲的摄取也是通过被动扩散进行的。
