Factors affecting the intestinal absorption of orally-administered physiologically active proteins in rat

我们观察到，给烫伤大鼠口服沙雷氏菌蛋白酶（SP，MW 50，600）可显著抑制烫伤引起的纤溶和血管通透性的增强，这有力地表明了它的肠道吸收。为了研究这种可能性，我们建立了一个高灵敏度的EIA和蛋白酶测定法测定大鼠血浆中的SP浓度，并成功地证明，口服给药的SP的一部分从肠道吸收的酶活性形式。这是第一次观察到口服生理活性蛋白质可以从肠道转移到血液中而不失去其原有的活性，最终在体内发挥系统功能，因此，我们一直试图确定可能控制大鼠肠道吸收SP程度的生理或营养因素。在先前的实验中，我们研究了年龄的影响， ...更多信息 并以吸收（A.Kakinuma：研究项目摘要，科学研究补助金（B）本研究的主要结果如下：1.分析了门静脉血浆SP浓度随时间的变化，结论：1.口服SP后，大鼠尾静脉血浆和肠系膜淋巴液中的SP含量明显增加，说明SP首先经淋巴液从肠道吸收，然后进入血液;给予SP溶液影响SP吸收的程度和模式。特别是60%（v/v）玉米油的存在使SP的吸收量增加了10倍以上，这是因为它将SP掺入到由油和水形成的乳状液中，使SP能够逃避胃酸变性和随后的蛋白酶降解（Biochem.Biophys.Res.Commun.31，488（1968））给出了与2.虽然SP在胃内（pH = 3）完全失活，但某些SP衍生分子（即预先失活的SP）被吸收并转移到血液中，并在血浆中被EIA检测到，其最大血药浓度在给药后1h达到最大值，比不加表面活性素时的2 h增加1.4-1.5倍。表面活性素除了影响SP在胃和肠中的稳定性外，还可能影响SP吸收的分子机制。少

Our observation that Serratia protease (SP,MW 50,600) orally-administered to scalded rats dramatically repressed the enhancement of fibrinolysis and blood vessel permeability both induced by the scalding, strongly suggested its intestinal absorption. To investigate this possibility, we established a highly-sensitive EIA and a protease assay for determining SP concentration in rat plasma, and succeeded in demonstrating that a portion of orally-administered SP was absorbed from the intestinal tract in an enzymatically active form. This was the first observation clearly indicating that orally-administered physiologically active proteins can be transferred from the intestine to the blood stream without losing its original activity to exert eventually a systemic function in the body.Since, we have been trying to identify any physiological or nutritional factors that may control the degree of the intestinal absorption of SP in rat. In the preious experiment, we investigated the effect of age … More and feeding on the absorption (A.Kakinuma : in Abstracts of Research Project, Grant-in-Aid for Scientific Research (B) (1995, Project No.06454083).Results of the present investigation are summarized as follows.1.We analyzed the time-course of the change of SP concentration in portal vein plasma, tail vein plasma and in mesenteric lymph after oral administration to know that SP is first absorbed from intestine by way of lymph and then transferred to blood.2.The coexistence of such substances as proteins and lipids in orally-administered SP solutions influenced the degree and the pattern of SP absorption. Especially, the presence of 60% (v/v) corn oil increased the amount of SP absorbed more than 10 times by incorporating SP into the emulsion formed by oil and water and enabling SP to escape from the denaturation by gastric acid and subsequent degradation by proteinases.3.Surfactin, an anionic peptidelipid surfactant produced by B.subtilis and isolated by us (Biochem.Biophys.Res.Commun.31,488 (1968)) gave an effect different from that of corn oil described in 2. Although SP administered together with surfactin was completely inactivated in stomach (pH3), some SP-derived molecule, presunably inactivated SP,was absorbed, transferred to blood and detected in plasma by our EIA.Its maximum plasma concentration, increased 1.4-1.5 times, was realized at 1h after administration, in contrast to 2h after adminstration in the absence of surfactin. Surfactin seems to influence the molecular mechanism of absorption of SP in addition to the stability of SP in stomach and intestine. Less