PROINSULIN, INSULIN, AND C-PEPTIDE CONCENTRATIONS IN HUMAN PORTAL AND PERIPHERAL-BLOOD
PROINSULIN, INSULIN, AND C-PEPTIDE CONCENTRATIONS IN HUMAN PORTAL AND PERIPHERAL-BLOOD
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DOI：
10.1172/jci108047
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发表时间：
1975-01-01
影响因子：
15.9
通讯作者：
RUBENSTEIN, AH
中科院分区：
文献类型：
--
作者：
HORWITZ, DL;STARR, JI;RUBENSTEIN, AH
测量了6名非糖尿病、非肥胖受试者门静脉和外周静脉血中胰岛素、胰岛素原和c肽的浓度。门静脉标本取脐静脉置管。3名受试者静脉输注25克葡萄糖，3名受试者静脉输注30克精氨酸。胰岛素和胰岛素原经凝胶过滤分离后用胰岛素免疫法测定，c肽用直接免疫法测定。在葡萄糖和精氨酸刺激下，所有三种肽的门静脉水平在刺激开始后90-120秒达到峰值。胰岛素浓度的相对升高幅度大于胰岛素原或c肽。外周静脉血中这三种肽的最高水平出现在较晚的时间（2-5分钟），胰岛素相对于胰岛素原和c肽的升高幅度较小。在分泌高峰时，门静脉胰岛素和c肽接近等摩尔浓度，而胰岛素原，根据胰岛素标准测量，约占总免疫反应性胰岛素的2.5%。在葡萄糖或精氨酸刺激后，门脉胰岛素、胰岛素原和c肽水平与同时绘制的外周样本中测量的浓度无关。然而，在所有采样时间，外周血和门静脉血中胰岛素和c肽之间都存在显著相关性。结果表明，在所研究的条件下，胰岛素和c肽在人体内以等摩尔浓度分泌，胰岛素原与胰腺中胰岛素的分泌比例相同。考虑到三种β细胞肽的相对分泌和代谢率，可以解释它们的外周浓度。这些数据进一步支持使用血浆c肽作为β细胞分泌功能的指标。
Concentrations of insulin, proinsulin, and C-peptide were measured in portal and peripheral venous blood in six nondiabetic, nonobese subjects. Portal vein samples were obtained by umbilical vein catheterization. Three subjects were studied with intravenous infusion of 25 g glucose, and three with 30 g arginine. Insulin and proinsulin were determined in the insulin immunoassay after separation by gel filtration, and C-peptide was measured by direct immunoassay. With both glucose and arginine stimulation, portal vein levels of all three peptides peaked at 90-120 s after the onset of the stimulus. Relative increases in insulin concentration were greater than those of proinsulin or C-peptide. In peripheral venous blood, maximal levels of the three peptides were observed later (2-5 min), and the increase in insulin relative toproinsulin and C-peptide was not as great. At the time of peak secretion, portal vein insulin and C-peptide approached equimolar concentrations, and proinsulin, as measured against an insulin standard, comprised approximately 2.5% of the total immunoreactive insulin. After stimulation by glucose or arginine, portal insulin, proinsulin and C-peptide levels were not correlated with the concentrations measured in simultaneously drawn peripheral samples. At all sampling times, however, significant correlation was found between insulin and C-peptide in both peripheral and portal blood. The results indicate that under the conditions studied, insulin and C-peptide are secreted in equimolar concentrations in man, and that proinsulin is secreted in the same proportion to insulin as found in the pancreas. Consideration of the relative secretory and metabolic rates of the three beta cell peptides explains their peripheral concentrations. The data further support the use of plasma C-peptide as an indicator of beta cell secretory function.