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

我们观察到烫伤大鼠口服沙雷氏菌蛋白酶（SP,MW 50,600）显著抑制了烫伤诱导的纤维蛋白溶解和血管通透性的增强，强烈提示其肠道吸收。为了研究这种可能性，我们建立了一种高灵敏度的EIA和蛋白酶测定法来测定大鼠血浆中的SP浓度，并成功地证明了部分口服SP以酶活性形式从肠道吸收。这是第一次清楚地表明口服生理活性蛋白质可以从肠道转移到血液中，而不会失去其最初的活性，最终在体内发挥全身功能。因此，我们一直在试图确定任何可能控制SP在大鼠肠道吸收程度的生理或营养因素。在之前的实验中，我们研究了年龄，More和饲养对吸收的影响(A.Kakinuma：在科研资助项目（B)(1995)，项目No.06454083）。本研究结果总结如下：1。我们通过对口服后门静脉血浆、尾静脉血浆及肠系膜淋巴中SP浓度变化的时间过程进行分析，得知SP首先通过淋巴从肠道吸收，然后转移到血液中。口服SP溶液中蛋白质和脂质等物质的共存影响SP的吸收程度和模式。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，这是由于SP加入到由油和水形成的乳状液中，使SP免于胃酸的变性和随后的蛋白酶的降解。表面素，一种由枯草芽孢杆菌产生的阴离子肽脂类表面活性剂（生物化学，生物物理，生物学报，31488）（1968）)产生的效果不同于第2章所述的玉米油。虽然SP与surfactin一起在胃中完全失活（pH3），但一些SP衍生的分子（可能是失活的SP）被吸收，转移到血液中，并通过我们的EIA在血浆中检测到。其血药浓度在给药后1h达到最大值，比不加表面素的给药后2h升高1.4 ~ 1.5倍。除了影响SP在胃和肠道的稳定性外，表面素似乎还影响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