Scheving L A, Yeh Y C, Tsai T H, Scheving L E
Endocrinology. 1980 May;106(5):1498-503. doi: 10.1210/endo-106-5-1498.
Epidermal growth factor (EGF) previously isolated from the submandibular salivary glands of mice was injected ip at five different circadian phases into separate sub-groups of adult male CD2F1 mice that had been standardized to 12 h of light alternating with 12 h of darkness. Comparable control groups were injected only with the carrier substance. Four, 8, and 12 h after each of the five injection times, subgroups of five mice were killed. Thirty minutes before sacrifice, each mouse was injected ip with 24 mu Ci tritiated thymidine ([3H]-TdR). Incorporation of [3H]TdR into the DNA of the duodenum, jejunum, ileum, cecum, colon, and rectum was determined. The results demonstrate for the first time that EGF has a stimulatory effect on DNA synthesis in these tissues, particularly in the colon and rectum. Under the conditions of this study, the stimulatory effects of EGF on DNA synthesis in the cecum, colon, and rectum were more dramatic than those in the three regions of the small intestine; in fact, DNA synthesis in the latter was occasionally statistically significantly decreased, particularly for mice killed during the dark phase. Stimulatory effects of EGF on DNA synthesis in the cecum, colon, and rectum were noticed as early as 4 h after injection; however, maximal stimulation occurred 8 and 12 h post injection.
先前从小鼠下颌下唾液腺中分离出的表皮生长因子（EGF），在五个不同的昼夜节律阶段经腹腔注射到成年雄性CD2F1小鼠的各个亚组中，这些小鼠已被标准化为12小时光照与12小时黑暗交替的环境。相应的对照组仅注射载体物质。在五个注射时间点中的每个时间点之后的4、8和12小时，将每组五只小鼠处死。在处死前30分钟，每只小鼠经腹腔注射24微居里的氚标记胸腺嘧啶核苷（[3H]-TdR）。测定[3H]TdR掺入十二指肠、空肠、回肠、盲肠、结肠和直肠DNA中的情况。结果首次表明，EGF对这些组织中的DNA合成具有刺激作用，尤其是在结肠和直肠中。在本研究条件下，EGF对盲肠、结肠和直肠中DNA合成的刺激作用比对小肠三个区域的刺激作用更为显著；事实上，小肠中DNA合成偶尔在统计学上显著降低，尤其是对于在黑暗阶段处死的小鼠。EGF对盲肠、结肠和直肠中DNA合成的刺激作用在注射后4小时就已出现；然而，最大刺激作用出现在注射后8和12小时。
