转化生长因子-β1在肝细胞性肝癌中表达增强

目的转化生长因子－β１（ＴＧＦβ１）在细胞生长的负性调节上有重要作用,是肝细胞生长和增殖的强抑制物但肝癌（ＨＣＣ）患者肝组织中ＴＧＦβ１ｍＲＮＡ表达高．现检测ＨＣＣ患者外周血中ＴＧＦβ１ｍＲＮＡ表达,血清ＴＧＦβ１水平,以及肝组织中ＴＧＦβⅡ型受体（ＴＧＦβＲⅡ）的表达．方法ＨＣＣ患者外周血分离单个核细胞（ＰＢＭＣ）,提取总ＲＮＡ,用反转录聚合酶链反应（ＲＴＰＣＲ）技术扩增ＴＧＦβ１ｍＲＮＡ．血清ＴＧＦβ１水平测定用Ｐｒｏｍｅｇａ公司产的试剂盒．肝组织ＴＧＦβＲⅡ表达的分析用原位杂交法．结果ＨＣＣ患者２０例ＰＢＭＣＴＧＦβ１ｍＲＮＡ用ＲＴＰＣＲ检测阳性率达７０％,对照组阴性．ＨＣＣ患者４０例血清ＴＧＦβ１水平（２７５８ｍｇ／Ｌ±８１０ｍｇ／Ｌ）明显高于对照组（８２７ｍｇ／Ｌ±３７２ｍｇ／Ｌ）．原位杂交表明,ＴＧＦβＲⅡ在ＨＣＣ细胞的胞质中有弱表达．结论ＨＣＣ患者ＴＧＦβ１基因在转录水平和翻译水平上均显示表达增强．ＰＢＭＣ有可能代替肝组织用以检测ＴＧＦβ１ｍＲＮＡ的表达应用于基础与临床的研究．     

骨关节炎滑膜细胞间粘附分子-1和转化生长因子-β1表达的研究

目的观察细胞间粘附分子１（ＩＣＡＭ１）和转化生长因子β１（ＴＧＦβ１）在骨关节炎（ＯＡ）患者滑膜中的表达,探讨ＩＣＡＭ１和ＴＧＦβ１在ＯＡ发病中的作用。方法应用免疫组织化学方法,对４０例骨关节炎滑膜和１８例类风湿关节炎（ＲＡ）滑膜中ＩＣＡＭ１和ＴＧＦβ１的分布进行观察。结果ＩＣＡＭ１表达于ＯＡ滑膜组织巨噬细胞样细胞、滑膜衬里细胞、成纤维细胞和血管内皮细胞。ＲＡ滑膜组织ＩＣＡＭ１表达部位和ＯＡ相似,但阳性程度和分布范围高于ＯＡ滑膜。ＴＧＦβ１表达于ＯＡ滑膜组织巨噬细胞样细胞,滑膜衬里细胞和成纤维细胞。ＲＡ滑膜组织ＴＧＦβ１染色分布和强度与ＯＡ相似。结论ＩＣＡＭ１可能通过免疫机制参与ＯＡ滑膜炎症反应;ＩＧＦβ１对ＯＡ滑膜炎症可能起抑制作用。     

Octreotide治疗Graves'眼病机理探讨

目的　探讨Ｏｃｔｒｅｏｔｉｄｅ 对细胞因子刺激后的人眼球后成纤维细胞的细胞间粘附分子１（ＩＣＡＭ１） 表达及ＤＮＡ 合成的影响。方法　应用细胞培养技术, 测定加入细胞因子及Ｏｃｔｒｅｏｔｉｄｅ后ＩＣＡＭ１ 表达和ＤＮＡ 合成情况。结果　ＴＮＦα（１０３ Ｕ／ｍｌ） 、γＩＮＦ（１００ Ｕ／ｍｌ） 和ＩＬ１β（１００ Ｕ／ｍｌ） 均能强烈刺激眼球后成纤维细胞表面ＩＣＡＭ１ 表达,而低浓度（ 即药理浓度）Ｏｃｔｒｅｏｔｉｄｅ 能明显地抑制这种刺激作用,但所需浓度及发挥抑制作用的时间各不相同;同样,低浓度Ｏｃｔｒｅｏｔｉｄｅ 也能抑制细胞因子（除ＩＬ１β外） 刺激的ＤＮＡ 合成。结论　Ｏｃｔｒｅｏｔｉｄｅ 治疗Ｇｒａｖｅｓ’眼病的作用途径部分是通过抑制细胞因子的作用,使ＩＣＡＭ１ 表达及ＤＮＡ 合成减少,它可能具有免疫调节的特性。     

卡介苗刺激的肺泡巨噬细胞上清液对肺成纤维细胞的作用

７．５－６０ｍｇ／Ｌ卡介苗（ＢＣＧ）刺激的肺泡巨噬细胞（ＰＡＭ）培养上清液能显著促进肺成纤维细胞（ＰＦＢ）增殖，发现上清液中含较高水平的肿瘤坏死因子（ＴＮＦ），且其促ＰＦＢ增殖作用与ＴＮＦ水平成正相关，提示ＢＣＧ在体外能刺激ＰＡＭ产生ＴＮＦ、ＴＮＦ为该上清液促ＰＦＢ增殖的主要因素。５０ｍｇ／ＬＳｉＯ２刺激的ＰＡＭ上清液亦能促进ＰＦＢ增殖，但上清液中几乎检测不到ＴＮＦ，说明其促ＰＦＢ增殖的成份是不同     

低分子肝素对aFGF促平滑肌细胞增殖作用的双相调节

探讨酸性成纤维细胞生长因子（ａＦＧＦ）与低分子肝素（ＬＭＷＨ）合用对主动脉平滑肌细胞（ＡＳＭＣ）增殖的影响。方法：在培养的兔ＡＳＭＣ中加入ａＦＧＦ及ＬＭＷＨ后，观察其对ＡＳＭＣ＾３Ｈ－Ｔ胸腺嘧啶脱氧核苷）掺入率的影响。结果：在培养的兔ＡＳＭＣ中加入ａＦＧＦ（１０ｎｇ／ｍｌ）后，ＡＳＭＣ的ＣＰＭ值明显增大，表明ａＦＧＦ具有促进ＡＳＭＣ增殖的作用。当在ａＦＧＦ为１０ｎｇ／ｍｌ的培养液中，加入ＬＭＷＨ后     

转化生长因子—β1单克隆抗体对大鼠肺纤维化的治疗观察

目的探讨转化生长因子－β（ＴＧＦ－β）单克隆抗体对博莱霉素所致肺间质纤维化的作用。方法结合体内和体外实验，利用３Ｈ－胸腺嘧啶核苷（３Ｈ－ＴｄＲ）掺入法和Ｎｏｒｔｈｅｒｎ杂交法。结果表明大鼠肺纤维化模型中肺泡巨噬细胞的条件培养基能促进成纤维细胞的增殖和胶原ｍＲＮＡ的表达。ＴＧＦ－β１单克隆抗体对其有抑制作用，同时亦能减轻肺组织的病变程度和胶原ｍＲＮＡ的表达。结论ＴＧＦ－β１单克隆抗体可部分地抑制成纤维细胞增殖和胶原合成。     

类风湿关节炎中转化生长因子β1和细胞间粘附分子的变化

目的：了解类风湿关节炎（ＲＡ）血清、滑液和滑膜组织中转化生长因β１（ＴＧＦβ１）、细胞间粘附分子１（ＩＣＡＭ１）及细胞间粘附分子３（ＩＣＡＭ３）的变化。方法：采用ＥＬＩＳＡ及ＡＢＣ免疫组化方法检测ＲＡ患者血清、滑液和滑膜中ＴＧＦβ１、ＩＣＡＭ１和ＩＣＡＭ３的浓度和阳性程度。结果：ＲＡ血清中ＴＧＦβ１含量较低，而ＩＣＡＭ１含量明显升高，ＩＣＡＭ３含量正常，滑液中ＩＣＡＭ３含量低于血清含量。ＲＡ血清中ＴＧＦβ１含量与ＩＣＡＭ１含量呈中度负相关，与ＩＣＡＭ３含量无显著相关。在ＲＡ滑膜中巨噬细胞、滑膜衬里细胞和成纤维细胞ＴＧＦβ１染色阳性，巨噬细胞、滑膜衬里细胞、成纤维细胞和血管内皮细胞ＩＣＡＭ１染色阳性。结论：ＴＧＦβ１和ＩＣＡＭ１参与了ＲＡ的发生和发展过程，在ＲＡ慢性炎症中，ＩＣＡＭ１对炎细胞转移并聚集于滑膜可能有重要作用，ＲＡ外周血ＴＧＦβ１浓度减低伴随ＩＣＡＭ１浓度的增加。     

血吸虫病肝纤维化患者转化生长因子β_1mRNA的水平及其临床意义

目的：研究血吸虫病患者 Ｔ Ｇ Ｆβ１ ｍ Ｒ Ｎ Ａ 水平及其临床意义。方法：用 Ｒ Ｔ Ｐ Ｃ Ｒ 加 ｄｏｔｂｌｏｔ法测定血吸虫病患者 Ｐ Ｂ Ｍ Ｃ中 Ｔ Ｇ Ｆβ１ ｍ Ｒ Ｎ Ａ 水平,与肝硬变和肝癌患者作比较,并研究了部分肝脏组织（肝癌患者１６ 例,肝血管瘤患者正常肝组织 ５ 例）中 Ｔ Ｇ Ｆβ１ ｍ Ｒ Ｎ Ａ 水平与 Ｐ Ｂ Ｍ Ｃ中水平的关系。同时,测定血清中 Ｈ Ａ、 Ｌ Ｎ、 ＣｏｌⅠⅤ和 Ｐ ＣⅢ水平,作为衡量肝纤维化活动与否的指标。结果： Ｐ Ｂ Ｍ Ｃ内 Ｔ Ｇ Ｆβ１ ｍ Ｒ Ｎ Ａ 水平在晚期血吸虫病患者组（ｎ＝ ２１,１２６±０１４）,肝硬变患者组（ｎ＝ １５,２０５±０８１）和肝癌患者组（ｎ＝ ２５,１８３±１２９）均显著高于正常对照组（ｎ＝ １６,０６２±０４０）（ Ｐ＜ ００５）。其中晚期血吸虫病患者组又显著低于肝硬变患者组或肝癌患者组（ Ｐ＜ ００５）,后两组差异无显著性（ Ｐ＞ ００５）。肝组织与 Ｐ Ｂ Ｍ Ｃ内 Ｔ Ｇ Ｆβ１ ｍ Ｒ Ｎ Ａ 水平差别无统计学意义（ Ｐ＞ ００５）。血清 Ｈ Ａ、 ＣｏｌⅣ和 Ｌ Ｎ 异常组的 Ｔ Ｇ Ｆβ１ ｍ Ｒ Ｎ Ａ 水平显著高于正常组（ Ｐ＜ ００５）。结论： Ｐ     

压力负荷增高性心肌肥厚大鼠心肌胶原网络重塑及其与内皮素的关系

目的探讨压力负荷增高性心肌肥厚大鼠心肌胶原网络的重塑及其与内皮素（ＥＴ）的可能关系。方法腹主动脉部分结扎致大鼠心肌肥厚，ＶＧ染色和图像处理观察心肌胶原网络重塑，放免测定心肌局部ＥＴ１含量，３Ｈ胸腺嘧啶（３ＨＴｄＲ）和３Ｈ脯氨酸参入试验观察心肌成纤维细胞的分裂增殖和胶原合成。结果手术组大鼠术后２周即出现明显左室肥厚，其程度随时间进展而加重。与假手术组比较，左室心肌总胶原容积百分比（ＣＶＦＴ）于术后２周增高，术后４、８周ＣＶＦＴ和无小血管视野ＣＶＦ（ＣＶＦＮＶ）均明显增高（Ｐ＜０．０１）。手术组大鼠左室心肌局部ＥＴ１含量明显高于相应假手术大鼠（Ｐ＜０．０１），且１０－１２～１０－８Ｍ浓度的ＥＴ１对培养心肌成纤维细胞３ＨＴｄＲ和３Ｈ脯氨酸的参入量有明显刺激作用，呈剂量依赖性。结论压力负荷增高性心肌肥厚形成过程中伴有心肌胶原网络重塑，心肌局部ＥＴ１含量增加可能与心肌胶原网络重构的形成有一定关系     

红霉素对肺纤维化大鼠核因子κB活性及细胞因子mRNA表达的影响

目的　探讨红霉素治疗肺纤维化的机制和疗效。方法　实验用Ｗｉｓｔａｒ 大鼠８１ 只，分成三组：正常对照组、博莱霉素模型组和红霉素治疗组， 每组２７ 只。气管内注入单剂量博莱霉素制备大鼠肺纤维化模型，于博莱霉素气管内注入后每日给予口服红霉素（１００ ｍｇ／ｋｇ）治疗，各组动物分别于气管内用药后第４、７ 和２８ 天处死动物。用凝胶电泳迁移实验测定肺泡巨噬细胞（ＡＭ） 的核因子（ＮＦ）κＢ活性；用Ｎｏｒｔｈｅｒｎ 杂交测定肺组织的白细胞介素１（ＩＬ１）β和转化生长因子（ＴＧＦ）βｍＲＮＡ表达。结果红霉素治疗组第４ 和第７ 天时，ＡＭ 的ＮＦκＢ活性与博莱霉素模型组比较，差异有显著性（Ｐ＜０－０５） ，第７ 天时肺组织的ＩＬ１β和ＴＧＦβｍＲＮＡ表达与博莱霉素模型组比较，差异有显著性（ Ｐ＜０－０５）。在病理上，红霉素减轻了肺泡炎及后续的肺纤维化。结论　在肺纤维化中，红霉素可能通过抑制ＮＦκＢ活性、ＩＬ１β和ＴＧＦβｍＲＮＡ表达起抗炎和抗纤维化作用。     

Transforming growth factor-beta stimulates production of insulin-like growth factor-binding protein-3 by human skin fibroblasts.

Human neonatal fibroblasts in monolayer culture produce insulin-like growth factor-binding protein-3 (IGFBP-3), the IGF-binding subunit of the circulating 140-kDa IGFBP complex. We now report that transforming growth factor-beta (TGF beta) is a potent stimulator of IGFBP-3 production by fibroblasts. After 72-h incubation with 1 ng/ml TGF beta, the levels of IGFBP-3 in conditioned medium were increased 5.8 +/- 1.2-fold (mean +/- SE; n = 9). Half-maximal stimulation of IGFBP-3 production was seen at 0.4 +/- 0.05 ng/ml TGF beta (n = 4). Coincubation of fibroblasts with TGF beta and either IGF-I or IGF-II at 50 ng/ml enhanced IGFBP-3 production 1.5- to 2-fold compared to TGF beta alone. As previously reported, fetal calf serum (FCS) stimulated IGFBP-3 production 5- to 6-fold; 1 ng/ml TGF beta increased the stimulated production of IGFBP-3 by FCS a further 2.5- to 3.5-fold. Acidification of FCS before addition enhanced the stimulation of IGFBP-3 compared to that caused by untreated FCS, but decreased further potentiation by TGF beta. This effect of acidified FCS was reversed by a neutralizing antibody to TGF beta. Similarly, the stimulation of IGFBP-3 levels by human serum or conditioned serum-free fibroblast medium was significantly increased by acidification of serum or medium before addition and was reversed by TGF beta antibody. These observations are consistent with acid-mediated activation of latent TGF beta added in serum or secreted by fibroblasts. Since IGFBP-3 is known to regulate IGF activity in fibroblasts, these results raise the possibility that TGF beta may modulate IGF actions in these cells by stimulating the production of IGFBP-3.     

The production of transforming growth factor-beta in the porcine ovary and its secretion in vitro

Porcine granulosa cells isolated from small (1-3 mm in diameter) follicles proliferate rapidly in culture in response to 10% fetal bovine serum (FBS) and epidermal growth factor (EGF) (10 ng/ml). Transforming growth factor-beta (TGF beta) inhibits FBS/EGF-stimulated proliferation in a dose-dependent manner. We have used this proliferation inhibitory property of TGF beta to assay qualitatively, the presence of this growth factor in conditioned medium from cultured follicle cells as well as in partially purified preparations from porcine ovarian compartments. In addition, the concentration of TGF beta in the theca cell conditioned medium was quantitatively estimated by generating a TGF beta-dose-response curve (inhibition of FBS/EGF-stimulated proliferation of granulosa cells in monolayer culture) using authentic human TGF beta-1. Ovarian thecal cells isolated from small and large size follicles in the pig ovary secrete TGF beta-like activity in vitro. Medium conditioned by thecal cells in primary monolayer culture contains a latent form of TGF beta which can be activated by heat or acid treatment. In contrast, and unlike rat granulosa cells, porcine granulosa cells in primary monolayer culture do not secrete detectable levels of TGF beta-like activity in the medium. Incubation of heat-activated thecal cell conditioned medium with a TGF beta-neutralizing antibody (which recognizes TGF beta-1 and 2) but not nonimmune serum attenuated the TGF beta-like activity in thecal cell conditioned medium suggesting that this activity is due to authentic TGF beta. Since many cell types secrete latent TGF beta in the medium when cultured in vitro, we next investigated whether thecal cell secretion of latent TGF beta was a function of cell culture or whether the ovarian thecal compartment actually contained detectable levels of TGF beta-like activity. To this end, we used an acid-ethanol extraction procedure to isolate thecal proteins from fresh-frozen tissue. The acid-ethanol extracted protein fraction was mixed with trace amounts of 125I-TGF beta for detection and chromatographed on Bio-Gel P-60 column under acidic conditions. Elution of TGF beta bioactivity from the Bio-Gel P-60 column as measured by inhibition of granulosa cell proliferation correlated with the elution of radioiodinated authentic TGF beta. Preincubation of TGF beta-like activity-containing fractions with TGF beta-neutralizing antibody attenuated the proliferation-inhibitory activity in these fractions. TGF beta activity was also observed in fractions extracted from porcine corpora lutea.(ABSTRACT TRUNCATED AT 400 WORDS)     

The production of transforming growth factor-beta by chick growth plate chondrocytes in short term monolayer culture

Transforming growth factor-beta (TGF beta) is capable of regulating the proliferation and phenotypic expression of growth plate chondrocytes in culture. Chondrocytes were isolated from the growth plates from the long bones of 3- to 5-week-old chicks. Conditioned medium was harvested from short term monolayer cultures for the assay of TGF beta production by these cells. A receptor competition assay using [125I]TGF beta was used to quantitate the amount of TGF beta in the conditioned medium. Acid-activated conditioned medium contained 5.0 +/- 0.4 ng/ml TGF beta, while conditioned medium that had not been exposed to acid had undetectable levels of the peptide by this assay. The initial cell plating density was inversely related to the amount of TGF beta produced on a per cell basis. Growth plate chondrocytes separated by countercurrent centrifugal elutriation into maturationally distinct subpopulations had different rates of TGF beta production; hypertropic chondrocytes produced significantly more TGF beta (4.5 ng/10(6) cells) than the smallest chondrocytes isolated (2.3 ng/10(6) cells). A variety of other growth mediators were tested for their ability to influence TGF beta production by chondrocytes, and it was found that only basic fibroblast growth factor could significantly influence TGF beta production, producing a 6-fold increase in TGF beta recovered in the conditioned medium. The production of TGF beta by growth plate chondrocytes implicates it as an important autocrine or paracrine regulator in the process of endochondral calcification.     

Stimulation of fibroblast collagen and total protein formation by an endothelial cell-derived factor

We investigated the effect of medium conditioned by bovine aortic endothelial cells on collagen accumulation and total protein formation by human embryonic fibroblasts or bovine smooth muscle cells in cultures. The conditioned medium at a 1:10 dilution induced a twofold increase in collagen and total protein accumulation in fibroblast cultures. At low concentration (1:50 dilution), the conditioned medium stimulated collagen accumulation preferentially; at high concentration (1:10 dilution), overall protein synthesis also was increased. The increase in type I collagen accumulation was associated with an increase in the steady-state level of alpha 1 (I) mRNA for collagen. The conditioned medium increased the production of types I and III collagen without affecting the proportion of collagen types in both fibroblast and smooth muscle cell cultures. Partial purification of the endothelial cell-derived factor disclosed it to be a heat-stable protein with an apparent molecular weight of 8-10 kDa. The stimulation of protein formation by this substance was not inhibited by antibodies against transforming growth factor-beta or the insulinlike growth factor I receptor. The partially purified factor stimulated protein production without affecting fibroblast proliferation. This endothelial cell-derived protein may play a role in the remodeling of vascular connective tissue by stimulating collagen synthesis.     

Effects of transforming growth factor-beta on matrix synthesis by chick growth plate chondrocytes

Transforming growth factor-beta (TGF beta) is a local regulator of cell metabolism and growth. TGF beta increases the synthesis of collagen and enhances the deposition of matrix by almost all cells studied to date. The presence of TGF beta in cartilage suggests an important autocrine function, and the present study was designed to examine its influence on the matrix synthesis of chick epiphyseal chondrocytes. Chondrocytes were plated in serum-free (BSA-supplemented) medium or medium containing 10% fetal bovine serum (FBS), and after 24 h in monolayer culture were treated with TGF beta in identical medium. A 24-h incubation with TGF beta caused a dose-dependent decrease in collagen synthesis (-14%) and increase in noncollagen protein synthesis (+25%), with greater effects in serum-containing medium (-22% and +58%, respectively). Similarly, the stimulation of sulfate incorporation by TGF beta was greater in FBS-containing medium (+140%) than in serum-free medium (+70%). These changes were present by 6 h, were maximal in the 0.3-3.0 ng/ml dose range, and were found to reflect an alteration in extracellular protein synthesis. The enhancement of TGF beta effects by serum was abolished when chondrocytes were plated and exposed to TGF beta in medium containing dialyzed FBS (12-14K membrane). The present study indicates that TGF beta influences the synthesis of matrix components by growth plate chondrocytes. The effects are enhanced by factors present in serum.     

Rat thecal/interstitial cells secrete a transforming growth factor-beta-like factor that promotes growth and differentiation in rat granulosa cells

Rat granulosa cells respond to transforming growth factor-beta (TGF beta) with increases in DNA synthesis and FSH-stimulated aromatase activity. To determine if the cells surrounding the granulosa cells generate TGF beta-like activity, which influences the growth and differentiation of granulosa cells, we cultured rat ovarian thecal/interstitial cells under serum-free conditions and collected their secretion products. Conditioned medium generated by primary cultures of thecal/interstitial cells over a 6-day collection period stimulated DNA synthesis, suggesting the presence of TGF beta-like bioactivity. At the onset of the collection period extracts of cultured cells contained undetectable levels of TGF beta-like activity, suggesting that the factor was produced and released by thecal/interstitial cells. FSH augmented the actions of both TGF beta and conditioned medium on DNA synthesis. Using an independent assay that relies on the response of the aromatase complex we showed that TGF beta and conditioned medium had parallel effects; TGF beta and conditioned medium alone did not influence the basal levels of aromatase activity, but both treatments augmented FSH-induced aromatase activity. Treatment of the conditioned medium with heat, acid, or alkali resulted in an increase in TGF beta-like bioactivity, suggesting that the TGF beta-like factor could be activated under these conditions. A commercially available antibody known to neutralize the bioactivity of TGF beta blocked the actions of TGF beta on DNA synthesis and blocked the growth-promoting activity of conditioned medium in a dose-dependent manner. Fractionation of the proteins in conditioned medium by elution through a Sephadex G-75 (superfine) column under acidic conditions showed that the growth-promoting activity and the aromatase activator eluted in fractions containing proteins with mol wt 25K. Standard TGF beta eluted in the same fractions. In summary, rat thecal/interstitial cells in culture secrete a TGF beta-like factor. The TGF beta-like factor may act together with FSH to promote growth and activate the aromatase complex of granulosa cells developing in the intrafollicular lumen in close association with the oocyte.     

Transforming growth factor-beta stimulates ascorbate transport activity in osteoblastic cells.

Transforming growth factor-beta (TGF beta) modulates the proliferation and differentiation of a number of cell types, including osteoblasts. TGF beta has been shown to stimulate matrix synthesis by connective tissue cells, but its mechanism of action is poorly understood. Because ascorbate (reduced vitamin C) also influences osteoblastic differentiation and is required as a cofactor for collagen synthesis, the present study examined the effect of TGF beta on osteoblastic ascorbate uptake. Saturable Na(+)-dependent uptake of ascorbate by cultures of UMR-106 rat osteosarcoma cells proceeded linearly with time for at least 10 min at 37 C. Exposure of cultures to TGF beta 1 stimulated initial rates of saturable Na(+)-dependent ascorbate transport, but did not affect nonspecific uptake or binding of the vitamin. Cells pretreated for 24 h with either vehicle or TGF beta 1 (3 ng/ml) and then assayed for transport of L-[14C] ascorbate (10 microM) showed significantly different transport activities (vehicle, 30 +/- 2; TGF beta 1, 44 +/- 3 nmol ascorbate/g protein/min; n = 14; P less than 0.005). Kinetic studies revealed that TGF beta 1 increased the maximum velocity of ascorbate transport without changing the affinity of the transporter for the vitamin, since the apparent maximum velocity increased from 83 to 106 nmol ascorbate/g protein/min; while the apparent Km remained unchanged at 20 microM L-ascorbate. The effect of this growth factor on ascorbate transport appeared to require protein synthesis, because it was completely blocked by cycloheximide. These results are consistent with TGF beta 1 increasing the rate of synthesis of either new Na+ ascorbate cotransporters or a regulatory protein that interacts with existing transporters to increase their turnover number. Enhanced uptake of ascorbate may contribute to the increase in collagen synthesis induced by TGF beta.     

Insulin-like growth factor-I (IGF-I) and transforming growth factor-beta 1 release IGF-binding protein-3 from human fibroblasts by different mechanisms.

Human neonatal fibroblasts in monolayer culture secrete insulin-like growth factor-binding proteins (IGFBPs), which may modulate IGF action. To examine whether an increase in extracellular concentrations of IGFBPs in response to IGF-I is due to the release of cell-associated IGFBPs, we measured secreted and cell-associated IGFBP-3 immunologically in fibroblast monolayers treated with IGF-I and IGF analogs with altered affinities for the IGF receptors and IGFBPs. IGFBP-3 in medium conditioned by fibroblasts treated with IGF-I was significantly increased (P < 0.05) compared with that in medium from untreated cultures; concomitantly, cell-associated IGFBP-3 was significantly decreased (P < 0.05). [Ser24]IGF-I (reduced affinity for IGF receptors) also increased secreted IGFBP-3 and decreased cell-associated IGFBP-3. In contrast, IGFBP-3 concentrations in medium conditioned by fibroblasts treated with B-chain IGF-I (reduced affinity for IGFBPs) were not significantly increased, and cell-associated IGFBP-3 was unchanged. Heparin, which releases proteins attached to cell surface proteoglycans, increased medium concentrations of IGFBP-3 and decreased IGFBP-3 binding to fibroblasts. An IGFBP of 29-31 kilodaltons (kDa) showed a pattern of regulation similar to that of IGFBP-3, while a third IGFBP, of 24 kDa, was decreased in IGF-I- and [Ser24]IGF-I-conditioned medium and unchanged by B-chain IGF-I and heparin. Preincubation with transforming growth factor-beta 1 (TGF beta 1), which stimulates fibroblast IGFBP-3 production, or human serum-derived IGFBP-3 did not increase cell-associated IGFBP-3. Analysis of total RNA isolated from fibroblasts revealed that IGFBP-3 mRNA was increased by TGF beta 1, but not by IGF-I. These data suggest that IGFs and TGF beta 1 release fibroblast IGFBPs by distinct mechanisms: IGFs by binding and subsequent release of cell-associated IGFBP-3 and 29- to 31-kDa IGFBP, and TGF beta 1 by increased de novo synthesis of IGFBP-3.