Kato Y, Koike T, Iwamoto M, Kinoshita M, Sato K, Hiraki Y, Suzuki F
Department of Biochemistry, Faculty of Dentistry, Osaka University, Japan.
Endocrinology. 1988 May;122(5):1991-7. doi: 10.1210/endo-122-5-1991.
Treatment of rabbit chondrocyte cultures with PTH or (Bu)2cAMP for 30 h increased by 2- to 3-fold the incorporation of [35S]sulfate and 3H radioactivity with glucosamine as the precursor into large chondroitin sulfate proteoglycans characteristically found in cartilage matrix. However, PTH and (Bu)2cAMP did not increase either [35S]sulfate incorporation into small proteoglycans or the incorporation of 3H radioactivity into hyaluronic acid and other glycosaminoglycans. PTH and (Bu)2cAMP also increased the incorporation of [3H] serine into both proteoglycans and total protein. In all cultures described above, the stimulation of [3H]serine incorporation into proteoglycans exceeded that of [3H]serine incorporation into total protein. These data indicate that PTH and (Bu)2cAMP selectively stimulate cartilage proteoglycan synthesis while they increase total protein synthesis. Since cAMP seems to play a mediatory role in the action of PTH, we elected to examine the effects of a limited exposure of chondrocytes to PTH or (Bu)2cAMP on the synthesis of proteoglycans. Treatment with PTH or (Bu)2cAMP for only the initial 2-7 h did not increase the rates of incorporation of [35S]sulfate, the 3H radioactivity with glucosamine, and [3H]serine into proteoglycans, as measured at 30 h, despite the fact that this treatment brought about a rapid and transient rise in the cAMP level. Furthermore, the application of prostaglandin I2 at concentrations that increased cAMP levels in a similar fashion as did PTH did not affect [35S] sulfate incorporation into proteoglycans. These observations suggest that in addition to the transient rise of cAMP, other biochemical changes are required for elaboration of the effect of PTH on proteoglycan synthesis. Although cAMP analogs mimic some of the effects of PTH in chondrocytes, the nucleotides and PTH appear to stimulate proteoglycan synthesis by different mechanisms.
用甲状旁腺激素（PTH）或双丁酰环磷腺苷（(Bu)2cAMP）处理兔软骨细胞培养物30小时，可使以葡萄糖胺为前体的[35S]硫酸盐和3H放射性掺入软骨基质中特有的大分子硫酸软骨素蛋白聚糖的量增加2至3倍。然而，PTH和(Bu)2cAMP既没有增加[35S]硫酸盐掺入小分子蛋白聚糖的量，也没有增加3H放射性掺入透明质酸和其他糖胺聚糖的量。PTH和(Bu)2cAMP还增加了[3H]丝氨酸掺入蛋白聚糖和总蛋白中的量。在上述所有培养物中，[3H]丝氨酸掺入蛋白聚糖的刺激作用超过了其掺入总蛋白的刺激作用。这些数据表明，PTH和(Bu)2cAMP在增加总蛋白合成的同时，选择性地刺激软骨蛋白聚糖的合成。由于环磷腺苷（cAMP）似乎在PTH的作用中起介导作用，我们选择研究软骨细胞有限暴露于PTH或(Bu)2cAMP对蛋白聚糖合成的影响。仅在最初的2至7小时用PTH或(Bu)2cAMP处理，在30小时时测量，并没有增加[35S]硫酸盐、以葡萄糖胺为前体的3H放射性以及[3H]丝氨酸掺入蛋白聚糖的速率，尽管这种处理导致cAMP水平迅速且短暂地升高。此外，以与PTH类似的方式增加cAMP水平的前列腺素I2的应用，并不影响[35S]硫酸盐掺入蛋白聚糖。这些观察结果表明，除了cAMP的短暂升高外，PTH对蛋白聚糖合成的作用还需要其他生化变化。尽管cAMP类似物模拟了PTH在软骨细胞中的一些作用，但核苷酸和PTH似乎通过不同的机制刺激蛋白聚糖的合成。
