Fang D, Dockery P, Weatherhead B
Department of Anatomy, The University of Hong Kong, Hong Kong.
Pigment Cell Res. 1998 Dec;11(6):337-44. doi: 10.1111/j.1600-0749.1998.tb00492.x.
The effects of alpha-MSH and cAMP on melanosomes in Cloudman S91 melanoma cells were investigated by modern stereological techniques. Cells were cultured for 4 days in medium containing alpha-MSH or cAMP, harvested at 24 hour intervals; some were frozen for melanin assay and the reminder embedded in Epon for light and electron microscopy. Cellular and melanosomal parameters were estimated by new stereological probes. We found that both stimulators induced increases in nuclear volume, cell volume, and the volume fractions and volumes of premelanosomes (V(Vpm,cell), Vpm) and mature melanosomes (V(Vmm,cell), Vmm), and the number of mature melanosomes (Nmm). Both stimulators also caused declines in the volume of individual mature melanosomes (V(Vimm)), the melanin content per mature melanosome unit volume and the melanin content per individual mature melanosome. The increases in the volume of individual premelanosomes and the number of premelanosomes were only induced by cAMP. The effect cAMP on some parameters occurred 24 hours prior to alpha-MSH and was more marked. The response of premelanosomes to the stimulators was more sensitive than mature melanosomes. These results suggest that both stimulators enhanced melanogenesis by increasing the V(Vpm,cell), V(Vmm,cell), Vpm, Vmm and Nmm. The melanogenic level did not depend on the V(Vimm) and melanin concentration in melanosomes. The maturation of premelanosomes was involved in melanogenesis induced by both stimulators, but, de novo synthesis and enlargement of premelanosomes were only stimulated by cAMP. It imply that exogenous cAMP may affect melanosomes, and hence melanogenesis in quantitatively or qualitatively different ways to alpha-MSH.
采用现代体视学技术研究了α-促黑素（α-MSH）和环磷酸腺苷（cAMP）对Cloudman S91黑色素瘤细胞中黑素小体的影响。将细胞在含有α-MSH或cAMP的培养基中培养4天，每隔24小时收获一次；部分细胞冷冻用于黑色素测定，其余细胞包埋于环氧树脂中用于光镜和电镜观察。通过新的体视学探针估计细胞和黑素小体参数。我们发现，两种刺激物均能诱导细胞核体积、细胞体积、前黑素小体（V（Vpm，cell），Vpm）和成熟黑素小体（V（Vmm，cell），Vmm）的体积分数和体积以及成熟黑素小体数量（Nmm）增加。两种刺激物还导致单个成熟黑素小体体积（V（Vimm））、每个成熟黑素小体单位体积的黑色素含量以及每个单个成熟黑素小体的黑色素含量下降。单个前黑素小体体积和前黑素小体数量的增加仅由cAMP诱导。cAMP对某些参数的影响比α-MSH提前24小时出现且更显著。前黑素小体对刺激物的反应比成熟黑素小体更敏感。这些结果表明，两种刺激物均通过增加V（Vpm，cell）、V（Vmm，cell）、Vpm、Vmm和Nmm来增强黑色素生成。黑色素生成水平不依赖于V（Vimm）和黑素小体中的黑色素浓度。两种刺激物诱导黑色素生成均涉及前黑素小体的成熟，但前黑素小体的从头合成和增大仅由cAMP刺激。这意味着外源性cAMP可能以与α-MSH在数量或质量上不同的方式影响黑素小体，进而影响黑色素生成。
