Madsen K, Friberg U, Roos P, Edén S, Isaksson O
Nature. 1983;304(5926):545-7. doi: 10.1038/304545a0.
The effect of growth hormone (GH) on various growth processes is generally considered to be indirect, mediated by GH-dependent plasma factors--somatomedins--which are produced mainly in the liver. In vitro, somatomedins stimulate a number of processes that apparently are associated with cell growth. It has been difficult, however, to induce skeletal growth by the administration of somatomedins in vivo. Daily injections of a partially purified somatomedin preparation failed to induce accumulated longitudinal bone growth using the intravital marker tetracycline or by measuring the nose-to-tail length. Administration of insulin-like growth factor I (IGF I) which is probably identical to somatomedin C, to hypophysectomized rats has been reported to increase the width of the epiphyseal plate. But although this suggests an in vivo effect of IGF I on longitudinal bone growth, such an effect has not been directly demonstrated. Recently, we reported that local administration of human GH (hGH) into the proximal cartilage growth plate of the tibia of hypophysectomized rats stimulated longitudinal bone growth on the side injected with the hormone. Furthermore, we have identified specific binding sites for hGH in cultured chondrocytes from rabbit ear and epiphyses. Here, we show that hGH, but not the structurally related polypeptides ovine prolactin or human prolactin, stimulates DNA synthesis in chondrocytes from rabbit ear and from rat rib growth plate, cultured in a chemically defined medium without the addition of serum. Our results suggest that GH directly initiates proliferation in mammalian chondrocytes.
生长激素（GH）对各种生长过程的影响通常被认为是间接的，由主要在肝脏产生的GH依赖性血浆因子——生长调节素介导。在体外，生长调节素刺激许多明显与细胞生长相关的过程。然而，在体内通过给予生长调节素诱导骨骼生长一直很困难。每日注射部分纯化的生长调节素制剂，无论是使用活体标记四环素还是测量鼻尖到尾尖的长度，都未能诱导累积的纵向骨生长。据报道，给垂体切除的大鼠注射可能与生长调节素C相同的胰岛素样生长因子I（IGF I），可增加骺板宽度。但尽管这表明IGF I对纵向骨生长有体内效应，但这种效应尚未得到直接证实。最近，我们报道向垂体切除大鼠胫骨近端软骨生长板局部注射人GH（hGH）可刺激注射激素一侧的纵向骨生长。此外，我们在兔耳和骨骺的培养软骨细胞中鉴定出了hGH的特异性结合位点。在此，我们表明，在不添加血清的化学限定培养基中培养时，hGH而非结构相关的多肽绵羊催乳素或人催乳素可刺激兔耳和大鼠肋骨生长板软骨细胞中的DNA合成。我们的结果表明，GH直接启动哺乳动物软骨细胞的增殖。
