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首页> 外文期刊>Pigment cell research >Melanogenic Response of the Kupffer Cells of Rana Esculenta L. to Melanocyte Stimulating Hormone
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Melanogenic Response of the Kupffer Cells of Rana Esculenta L. to Melanocyte Stimulating Hormone

机译：毛ana林的枯否细胞对黑素细胞刺激激素的黑素反应。

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We have previously shown that Kupffer cells (KCs) of Rana esculenta L. possess melanogenic ability. The melanogenic enzyme activities in these cells are different from those described in skin melanocytes, and very little is known about their regulation by extracellular signalling molecules. In order to study this regulation, we analysed the effects of NDP-MSH on the levels of expression of the tyrosinase gene and on dopa-oxidase activity, using primary cultures of KCs. Incubation of the cells with NDP-MSH increases tyrosinase gene transcription, within the first 24 h of stimulation. To gain insight into the signalling mechanism involved in the cell response to the hormone, KCs in culture were incubated with IBMX or forskolin. These agents mimic the effects of a-MSH on melanocytes by increasing the intracellular level of cAMP. The experimental results showed that while the hormonal treatment always activated the KC tyrosinase system, treatment with IBMX or forskolin never did. Therefore, in KCs the tyrosinase-stimulating action of NDP-MSH was not mimicked by cAMP elevating agents. Assays of cAMP levels in cells stimulated with NDP-MSH demonstrated that the hormone does not produce significant increases in intracellular cAMP. On the contrary, forskolin produced significant increases in cAMP starting from 30 min of incubation. These results suggest that tyrosinase induction by melanocortins in KCs is not mediated by the cAMP pathway, and highlight the existence of substantial differences in the hormone signal transduction mechanisms between amphibian KCs and melanocytes or melanoma cells.
机译：先前我们已经表明，食用蛙（Rana esculenta L.）的库普弗细胞（KCs）具有黑色素生成能力。这些细胞中的黑色素生成酶活性与皮肤黑色素细胞中描述的不同，对细胞外信号分子对它们的调控知之甚少。为了研究此调控，我们使用KCs的原代培养物分析了NDP-MSH对酪氨酸酶基因表达水平和对多巴氧化酶活性的影响。在刺激的最初24小时内，用NDP-MSH孵育细胞会增加酪氨酸酶基因的转录。为了深入了解细胞对激素的反应所涉及的信号传导机制，将培养的KC与IBMX或毛喉素一起孵育。这些药物通过增加细胞内cAMP水平来模拟a-MSH对黑素细胞的作用。实验结果表明，尽管激素治疗总是能激活KC酪氨酸酶系统，但用IBMX或福司可林治疗却从未如此。因此，在KC中，cAMP升高剂不能模仿NDP-MSH的酪氨酸酶刺激作用。用NDP-MSH刺激的细胞中cAMP水平的测定表明，该激素不会在细胞内cAMP中产生明显的增加。相反，从孵育30分钟开始，福司可林产生的cAMP显着增加。这些结果表明，黑皮皮质素在KCs中诱导酪氨酸酶不是由cAMP途径介导的，并且突显了两栖KCs与黑素细胞或黑素瘤细胞之间激素信号转导机制的实质差异。

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