King G L, Goodman A D, Buzney S, Moses A, Kahn C R
J Clin Invest. 1985 Mar;75(3):1028-36. doi: 10.1172/JCI111764.
It has been suggested that elevated levels of insulin or insulin-like growth factors (IGFs) play a role in the development of diabetic vascular complications. Previously, we have shown a differential response to insulin between vascular cells from retinal capillaries and large arteries with the former being much more insulin responsive. In the present study, we have characterized the receptors and the growth-promoting effect of insulinlike growth factor I (IGF-I) and multiplication-stimulating activity (MSA, an IGF-II) on endothelial cells and pericytes from calf retinal capillaries and on endothelial and smooth muscle cells from calf aorta. We found single and separate populations of high affinity receptors for IGF-I and MSA with respective affinity constants of 1 X 10(-9) M-1 and 10(-8) M-1 in all four cell types studied. Specific binding of IGF-I was between 7.2 and 7.9% per milligram of protein in endothelial cells and 9.1 and 10.4% in the vascular supporting cells. For 125I-MSA, retinal endothelial cells bound only 1.7-2.5%, whereas the aortic endothelial cells and the vascular supporting cells bound between 5.6 and 8.5% per milligram of protein. The specificity of the receptors for IGF-I and MSA differed, as insulin and MSA was able to compete with 125I-IGF-I for binding to the IGF-I receptors with 0.01-0.1, the potency of unlabeled IGF-I, whereas even 1 X 10(-6) M, insulin did not significantly compete with 125I-MSA for binding to the receptors for MSA. For growth-promoting effects, as measured by the incorporation of [3H]thymidine into DNA, confluent retinal endothelial cells responded to IGF-I and MSA by up to threefold increase in the rate of DNA synthesis, whereas confluent aortic endothelial cells did not respond at all. A similar differential of response to insulin between micro- and macrovascular endothelial cells was reported by us previously. In the retinal endothelium, insulin was more potent than IGF-I and IGF-I was more potent that MSA. In the retinal and aortic supporting cells, no differential response to insulin or the IGFs was observed. In the retinal pericytes, IGF-I, which stimulated significant DNA synthesis beginning at 1 X 10(-9) M, and had a maximal effect at 5 X 10(-8) M, was 10-fold more potent than MSA and equally potent to insulin. In the aortic smooth muscle cells, IGF-I was 10-100 times more potent than insulin or MSA. In the retinal and aortic supporting cells, no differential response to insulin or the IGFs was observed. In the retinal pericytes, IGF-I, which stimulated significant DNA synthesis beginning at 1 X 10(-9) M, and had a maximal effect at 5 X 10(-8) M, was 10-fold more potent than MSA and equally potent to insulin. In the aortic smooth muscle cells, IGF-I was 10-100 times more potent than insulin or MSA. In addition, insulin and IGF-I at 1 X 10(-6) and 1 X 10(-8) M, respectively, stimulated these cells to grow by doubling the number of cells as well. In all responsive tissues, the combination of insulin and IGFs were added together, no further increase in effect was seen. These data showed that vascular cells have insulin and IGF receptors, but have a differential response to these hormones. These differences in biological response between cells from retinal capillaries and large arteries could provide clues to understanding the pathogenesis of diabetic micro- and macroangiopathy.
有人提出，胰岛素或胰岛素样生长因子（IGFs）水平升高在糖尿病血管并发症的发生发展中起作用。此前，我们已表明视网膜毛细血管和大动脉的血管细胞对胰岛素的反应存在差异，前者对胰岛素的反应性更强。在本研究中，我们已对胰岛素样生长因子I（IGF-I）和增殖刺激活性（MSA，一种IGF-II）对小牛视网膜毛细血管的内皮细胞和周细胞以及小牛主动脉的内皮细胞和平滑肌细胞的受体和促生长作用进行了表征。我们发现在所有四种研究的细胞类型中，IGF-I和MSA存在单一且不同的高亲和力受体群体，其各自的亲和常数分别为1×10⁻⁹ M⁻¹和10⁻⁸ M⁻¹。IGF-I的特异性结合在内皮细胞中为每毫克蛋白质7.2%至7.9%，在血管支持细胞中为9.1%至10.4%。对于¹²⁵I-MSA，视网膜内皮细胞仅结合1.7% - 2.5%，而主动脉内皮细胞和血管支持细胞每毫克蛋白质结合5.6%至8.5%。IGF-I和MSA受体的特异性不同，因为胰岛素和MSA能够以未标记IGF-I效力的0.01 - 0.1与¹²⁵I-IGF-I竞争结合IGF-I受体，而即使是1×10⁻⁶ M的胰岛素也不能与¹²⁵I-MSA显著竞争结合MSA受体。对于促生长作用，通过[³H]胸腺嘧啶掺入DNA来测量，汇合的视网膜内皮细胞对IGF-I和MSA的反应是DNA合成速率增加高达三倍，而汇合的主动脉内皮细胞根本没有反应。我们之前报道过微血管和大血管内皮细胞对胰岛素的反应也存在类似差异。在视网膜内皮中，胰岛素比IGF-I更有效，而IGF-I比MSA更有效。在视网膜和主动脉支持细胞中，未观察到对胰岛素或IGFs的差异反应。在视网膜周细胞中，IGF-I从1×10⁻⁹ M开始刺激显著的DNA合成，在5×10⁻⁸ M时具有最大效应，其效力比MSA高10倍，与胰岛素相当。在主动脉平滑肌细胞中，IGF-I比胰岛素或MSA强10 - 100倍。在视网膜和主动脉支持细胞中，未观察到对胰岛素或IGFs的差异反应。在视网膜周细胞中，IGF-I从1×10⁻⁹ M开始刺激显著的DNA合成，在5×10⁻⁸ M时具有最大效应，其效力比MSA高10倍，与胰岛素相当。在主动脉平滑肌细胞中，IGF-I比胰岛素或MSA强10 - 100倍。此外，分别为1×10⁻⁶ M和1×10⁻⁸ M的胰岛素和IGF-I也刺激这些细胞生长，使细胞数量增加一倍。在所有反应性组织中，将胰岛素和IGFs组合添加在一起，未观察到效果进一步增加。这些数据表明血管细胞具有胰岛素和IGF受体，但对这些激素有不同的反应。视网膜毛细血管和大动脉细胞之间生物学反应的这些差异可能为理解糖尿病微血管和大血管病变的发病机制提供线索。
