Absence of ultradian rhythm or diurnal variation in insulin-like growth factor-I in rats.
Absence of ultradian rhythm or diurnal variation in insulin-like growth factor-I in rats.
复制标题
大鼠胰岛素样生长因子-I 不存在超昼夜节律或昼夜变化。
DOI：
10.1159/000125530
复制
发表时间：
1990
影响因子：
4.1
通讯作者：
Russell,WE
中科院分区：
文献类型：
--
作者：
Donaghue,KC;Badger,TM;Millard,WJ;Frisch,LS;Russell,WE
我们研究了血浆胰岛素样生长因子-I（IGF-I）浓度的变化在不受限制，插管大鼠。为了检测快速变化，每15分钟对6只大鼠取样，持续6小时。在酸-乙醇（AE）提取之前和之后测定血浆中的生长激素（GH）和IGF-I，以减少血浆结合蛋白的掩蔽效应。AE使新鲜采集的大鼠血清和肝素化血浆的免疫反应性增加3倍，但在-20 ℃下储存4周后对血清无影响。相比之下，肝素化血浆在采集后数月内保持对AE的敏感性。AE提取的血清在效力上与进行酸性凝胶层析的血清相同。GH每3.3 ± 0.15 h出现一次高幅同步脉冲。尽管IGF-I浓度的变化类似于脉动，但当未提取和AE提取血浆的数据经过2种旨在检测激素脉冲的计算机算法时，在24个系列分析中的8个中未识别出脉冲。这两个程序在未提取血浆中识别脉冲时仅同时发生4次，并且仅在一种情况下，在给定样本的未提取和AE提取血浆中识别出脉冲。Santen和Bardin（S&B）程序对单个血清样本重复测定的假阳性率为11%，而梅里亚姆和Wachter（M&W）程序的假阳性率小于10%。在6小时的采样时间内，或在1或2小时的滞后期后，GH和IGF-I浓度总和之间无正相关性。为了检测昼夜变化，第二组5只大鼠每2小时取样一次，持续36小时。这些动物的IGF-I浓度波动很小，光照期和黑暗期之间没有差异。我们的研究没有提供证据表明IGF-I的间歇性释放或昼夜变化夹带到光或喂养周期。
We studied the variation in plasma insulin-like growth factor-I (IGF-I) concentrations in unrestrained, cannulated rats. To detect rapid changes, 6 rats were sampled every 15 min for 6 h. Plasma was assayed for growth hormone (GH), and for IGF-I before and after acid-ethanol (AE) extraction to reduce the masking effect of plasma binding proteins. AE increased the immunoreactivity of freshly collected rat serum and heparinized plasma by 3-fold, but had no effect on serum after 4 weeks of storage at -20 ° C. In contrast, heparinized plasma maintained its sensitivity to AE for many months after collection. AE-extracted serum was identical in potency to serum that was subjected to acid gel chromatography. GH showed high amplitude, synchronized pulses every 3.3 ± 0.15 h. Despite variations in IGF-I concentrations that resembled pulsations, when the data from both unextracted and AE-extracted plasma were subjected to 2 computer algorithms designed to detect hormone pulses, no pulses were identified in 8 of the 24 series of analyses. The two programs concurred only 4 times in their identification of a pulse in unextracted plasma, and in only one instance was a pulse identified in both unextracted and AE-extracted plasma from a given sample. Based on repeated measurements of a single serum sample, the program of Santen and Bardin (S&B) had a false-positive rate of 11 %, and that of Merriam and Wachter (M&W) less than 10%. There was no positive correlation between summed GH and IGF-I concentrations over the 6 h of sampling, or after a 1- or 2-hour lag period. To detect diurnal variations, a second group of 5 rats was sampled every 2 h for 36 h. These animals showed little fluctuation of IGF-I concentrations and no differences between the light and dark periods. Our studies provide no evidence for episodic release of IGF-I or diurnal variations entrained to light or feeding cycles.