Clemmons D R, Underwood L E, Van Wyk J J
J Clin Invest. 1981 Jan;67(1):10-9. doi: 10.1172/JCI110001.
Human growth hormone (hGH) is known to be a potent stimulator of somatomedin secretion in vivo. The induction of somatomedin by growth hormone has been difficult to study in vitro, however, because no organ containing a high concentration of somatomedin has been identified. Because fetal mouse explants have been shown to produce somatomedin in vitro, we have undertaken studies to determine whether postnatal human fibroblast monolayers also produce somatomedin, and if so, whether its production is regulated by other hormones. Quiescent human fibroblasts were exposed to serum-free minimum essential medium, and the medium was assayed for somatomedin concentration using a specific radioimmunoassay for somatomedin-C. A progressive rise in immunoreactive somatomedin to 0.08 U/ml per 10(5) cells per 24 h was observed over 72 h of incubation. This was an underestimation of the actual concentration of immunoreactive somatomedin since the amount measured following acid treatment was at least fourfold higher than in the untreated medium. Growth hormone stimulated immunoreactive somatomedin production in a dose-dependent manner: 5 ng hGH/ml = 0.1 U/ml per 10(5) cells; 50 ng hGH/ml = 0.25 U/ml per 10(5) cells. Platelet-derived growth factor and fibroblast growth factor were also stimulatory, but epidermal growth factor, thyroxine, or cortisol had no effect. Media that had been exposed to human fibroblasts stimulated DNA synthesis in BALB/c 3T3 fibroblasts (a cell type that does not produce somatomedin). Medium-derived immuno-reactive somatomedin eluted from Sephacryl S-200 in two major peaks (150,000 and 8,000 mol wt). The higher molecular weight peak is similar to the one observed when whole serum was used. These studies provide a model system for studying the humoral and nonhumoral factors that control the biosynthesis of somatomedin by human tissues. Since immunoreactive somatomedin production may be a rate-limiting factor for fibroblast growth, the delineation of the hormonal control of somatomedin production should lead to a better understanding of the mechanisms controlling human fibroblast growth.
已知人类生长激素（hGH）在体内是促生长因子分泌的有效刺激物。然而，生长激素诱导促生长因子的过程在体外很难研究，因为尚未发现含有高浓度促生长因子的器官。由于已证明胎鼠外植体在体外可产生促生长因子，我们开展了研究，以确定出生后的人成纤维细胞单层是否也能产生促生长因子，若能产生，其产生过程是否受其他激素调控。将静止的人成纤维细胞暴露于无血清的最低必需培养基中，然后使用针对促生长因子-C的特异性放射免疫测定法检测培养基中的促生长因子浓度。在72小时的孵育过程中，观察到免疫反应性促生长因子每24小时每10⁵个细胞逐渐升高至0.08 U/ml。这是对免疫反应性促生长因子实际浓度的低估，因为酸处理后测得的量比未处理的培养基中至少高四倍。生长激素以剂量依赖的方式刺激免疫反应性促生长因子的产生：5 ng hGH/ml = 每10⁵个细胞0.1 U/ml；50 ng hGH/ml = 每10⁵个细胞0.25 U/ml。血小板衍生生长因子和成纤维细胞生长因子也具有刺激作用，但表皮生长因子、甲状腺素或皮质醇则无作用。暴露于人成纤维细胞的培养基可刺激BALB/c 3T3成纤维细胞（一种不产生促生长因子的细胞类型）中的DNA合成。从Sephacryl S - 200洗脱的培养基衍生免疫反应性促生长因子有两个主要峰（分子量分别为150,000和8,000）。较高分子量的峰与使用全血清时观察到的峰相似。这些研究提供了一个模型系统，用于研究控制人体组织中促生长因子生物合成的体液和非体液因素。由于免疫反应性促生长因子的产生可能是成纤维细胞生长的限速因素，阐明促生长因子产生的激素调控应有助于更好地理解控制人成纤维细胞生长的机制。
