Guzelian P S, Lindblad W J, Diegelmann R F
Gastroenterology. 1984 May;86(5 Pt 1):897-904.
We have established previously that the adult rat hepatocyte produces collagen under conditions of primary monolayer culture or under pathologic conditions in vivo. During the initial 3 days of incubation of hepatocytes in serum-free culture medium, collagen synthesis represented only 0.01%-0.05% of the synthesis of noncollagen proteins. Thereafter, rates of collagen synthesis rose dramatically, and after 9 days of incubation were increased an average tenfold in cultures derived from normal hepatocytes and 30-fold in cultures derived from regenerated liver. The spontaneous increase in the rates of collagen synthesis was almost completely blocked (94%) when cultures were incubated for 8 days in medium containing the synthetic glucocorticoid dexamethasone (10(-7) M). Dexamethasone was without effect on the synthesis of noncollagen proteins. Inhibition of collagen synthesis by dexamethasone exhibited a sigmoidal dose-response curve with 50% inhibition observed at a concentration of 10(-9) M. Collagen synthesis was diminished similarly by other glucocorticoids (hydrocortisone, methylprednisolone, triamcinolone, prednisone, all 10(-6) M) but not by other hormonal or nonhormonal steroids (progesterone, estradiol, testosterone, all 10(-5) M). We excluded increased collagen degradation as an explanation for these results by demonstrating that dexamethasone failed to increase the incorporation of radioactive proline into trichloroacetic acid-soluble radioactive hydroxyproline. Exposure of hepatocytes to dexamethasone during the first 48 h of incubation produced inhibition of collagen synthesis in 9-day-old cultures, even though washout studies with [3H]dexamethasone revealed negligible retention of the steroid by the cells. This observation suggests that among the initial, culture-adaptive responses of the hepatocyte are glucocorticoid-sensitive events that culminate in increased rates of collagen synthesis days later. We conclude that glucocorticoids may serve as natural suppressors of the potential of the hepatocyte to produce collagen.
我们先前已经证实，成年大鼠肝细胞在原代单层培养条件下或体内病理条件下会产生胶原蛋白。在无血清培养基中培养肝细胞的最初3天内，胶原蛋白合成仅占非胶原蛋白合成的0.01% - 0.05%。此后，胶原蛋白合成速率急剧上升，培养9天后，来自正常肝细胞的培养物中胶原蛋白合成平均增加了10倍，来自再生肝的培养物中增加了30倍。当培养物在含有合成糖皮质激素地塞米松（10^(-7) M）的培养基中培养8天时，胶原蛋白合成速率的自发增加几乎完全被阻断（94%）。地塞米松对非胶原蛋白的合成没有影响。地塞米松对胶原蛋白合成的抑制呈现出S形剂量反应曲线，在浓度为10^(-9) M时观察到50%的抑制。其他糖皮质激素（氢化可的松、甲泼尼龙、曲安西龙、泼尼松，均为10^(-6) M）对胶原蛋白合成的抑制作用类似，但其他激素或非激素类固醇（孕酮、雌二醇、睾酮，均为10^(-5) M）则无此作用。我们通过证明地塞米松未能增加放射性脯氨酸掺入三氯乙酸可溶性放射性羟脯氨酸来排除胶原蛋白降解增加作为这些结果的解释。在培养的最初48小时内将肝细胞暴露于地塞米松会抑制9天大的培养物中的胶原蛋白合成，尽管用[3H]地塞米松进行的洗脱研究显示细胞对该类固醇的保留可忽略不计。这一观察结果表明，在肝细胞最初的培养适应性反应中，存在糖皮质激素敏感事件，这些事件最终在数天后导致胶原蛋白合成速率增加。我们得出结论，糖皮质激素可能作为肝细胞产生胶原蛋白潜力的天然抑制剂。
