Kaplan J, Keogh E A
Cell. 1981 Jun;24(3):925-32. doi: 10.1016/0092-8674(81)90118-5.
Incubation of rabbit alveolar macrophages in vitro with methyl amine led to a time- and concentration-dependent inhibition of uptake of alpha macroglobulin-125I-trypsin complexes (alpha M-125I-T). Upon addition of methyl amine (50 mM) to cells prelabeled with alpha M-125I-T there was a rapid inhibition of lysosomal catabolism of internalized ligand. In the absence of ligand, incubation of cells with 50 mM methyl amine led to a 40-70% decrease in surface-receptor number. The methyl amine-induced decrease in surface-receptor number only occurred in metabolically active cells since cells incubated at 0 degrees C, or treated with N-ethyl maleimide and incubated at 37 degrees C, did not show the effect. Incubation of cells at 37 degrees C with methyl amine also effected a 40-70% decrease in fluid-phase pinocytosis. Although there was a decline in surface-receptor number, the remaining population of receptors were capable of mediating (at least) one round of ligand internalization. However, further ligand uptake was prevented. Data demonstrate that although receptors were present on cell surfaces, they were incapable of mediating ligand internalization. Incubation of macrophages with chloroquine at 37 degrees C for 60 min also led to a disappearance of receptors, and a concomitant reduction in fluid-phase pinocytosis.
用甲胺在体外孵育兔肺泡巨噬细胞，会导致α巨球蛋白 - 125I - 胰蛋白酶复合物（αM - 125I - T）摄取受到时间和浓度依赖性抑制。向预先用αM - 125I - T标记的细胞中加入甲胺（50 mM）后，内化配体的溶酶体分解代谢迅速受到抑制。在没有配体的情况下，用50 mM甲胺孵育细胞会导致表面受体数量减少40 - 70%。甲胺诱导的表面受体数量减少仅发生在代谢活跃的细胞中，因为在0℃孵育的细胞，或用N - 乙基马来酰亚胺处理并在37℃孵育的细胞，均未表现出这种效应。在37℃用甲胺孵育细胞也会使液相胞饮作用减少40 - 70%。虽然表面受体数量有所下降，但剩余的受体群体仍能够介导（至少）一轮配体内化。然而，进一步的配体摄取被阻止。数据表明，尽管受体存在于细胞表面，但它们无法介导配体内化。在37℃用氯喹孵育巨噬细胞60分钟也会导致受体消失，并伴随液相胞饮作用减少。
