Raaberg L, Nexø E, Tollund L, Poulsen S S, Christensen S B, Christensen M S
Department B, University of Copenhagen, Panum Institute, Denmark.
Regul Pept. 1990 Sep 10;30(2):149-57. doi: 10.1016/0167-0115(90)90055-2.
The concentration of EGF immunoreactivity in rat whey increases from 0.3 pmol/ml at lactation day 1 to 2.0 pmol/ml at lactation day 19. The concentration of EGF is not influenced when the rats undergo sialoadenectomy prior to mating. On S-200 gel chromatography, almost all EGF-reactivity in rat whey elutes as a broad peak corresponding to a Stokes radius of 4.0 nm (an approximate molecular weight of 80 kDa). Almost no 6 kDa EGF is present. Judged by gel filtration of whey pre-incubated with 125I-EGF (6 kDa), no binding protein for EGF is present in rat whey. When rat milk is incubated overnight at 37 degrees C, the 80 kDa EGF is degraded and elutes as a peak with a Stokes radius of 2.7 nm, corresponding to a molecular weight of approximately 35 kDa EGF and as a peak corresponding to 6 kDa EGF. Also, after partial purification by immuno-affinity chromatography, the EGF-reactive material in rat whey behaves as a peptide with a Stokes radius of 2.7 nm, corresponding to a molecular weight of approximately 35 kDa at gel filtration. Comparative binding studies between EGF purified from the submandibular glands and the EGF purified from rat whey confirm differences in the binding to antibodies raised against submandibular EGF, but not in binding to the EGF-receptor. Our results make it unlikely that EGF in rat whey is derived from the submandibular glands.
大鼠乳清中表皮生长因子（EGF）免疫反应性的浓度从哺乳期第1天的0.3皮摩尔/毫升增加到哺乳期第19天的2.0皮摩尔/毫升。在交配前对大鼠进行涎腺切除术后，EGF的浓度不受影响。在S-200凝胶色谱上，大鼠乳清中几乎所有的EGF反应性都以一个宽峰形式洗脱出来，其斯托克斯半径为4.0纳米（近似分子量为80 kDa）。几乎不存在6 kDa的EGF。通过对与125I-EGF（6 kDa）预孵育的乳清进行凝胶过滤判断，大鼠乳清中不存在EGF结合蛋白。当大鼠乳汁在37℃下孵育过夜时，80 kDa的EGF会降解，并以斯托克斯半径为2.7纳米的峰形式洗脱出来，对应于分子量约为35 kDa的EGF，同时还有一个对应于6 kDa EGF的峰。此外，经过免疫亲和色谱部分纯化后，大鼠乳清中具有EGF反应性的物质在凝胶过滤时表现为一种肽，其斯托克斯半径为2.7纳米，对应于分子量约为35 kDa。从颌下腺纯化的EGF与从大鼠乳清中纯化的EGF之间的比较结合研究证实，它们与针对颌下EGF产生的抗体的结合存在差异，但与EGF受体的结合没有差异。我们的结果表明，大鼠乳清中的EGF不太可能来自颌下腺。
