de Graan P N, Molenaar R, van de Veerdonk F C
Mol Cell Endocrinol. 1983 Oct;32(2-3):271-84. doi: 10.1016/0303-7207(83)90088-6.
A new in vitro melanophore system is described, which employs pieces from the ventral tail-fin of Xenopus laevis tadpoles. Tail-fin melanophores in vitro retain the ability to disperse their pigment in darkness and to reaggregate it upon illumination. In the light, alpha-MSH, cAMP, dibutyryl-cAMP and theophylline induce a concentration-dependent pigment dispersion. The log dose-response curve obtained with alpha-MSH is sigmoidal with a linear portion between 0.5 and 2.0 ng alpha-MSH/ml. In this range, the log dose-response curve can be used as the standard curve in a bioassay for melanotropic activity, applying either the melanophore index (assay I) or a photometric transmittance measurement (assay II) for the quantification of the melanophore response. To prevent interference from the light/darkness response, light of 400-500 nm (to which the melanophores are most sensitive) was used during the assay. Both assays show high precision (lambda I = 0.13, lambda II = 0.11). Several peptides derived from alpha-MSH were tested for their melanotropic activity. The in vitro Xenopus melanophore system offers unique properties for the study of alpha-MSH action: (1) the melanophore system is uncontaminated with other chromatophores; (2) to date it is the only system suitable for photoaffinity labelling of alpha-MSH receptors; and (3) the melanophore receptor requirements differ from those of Rana.
本文描述了一种新的体外黑素细胞系统，该系统使用非洲爪蟾蝌蚪腹侧尾鳍的片段。体外尾鳍黑素细胞保留了在黑暗中分散色素并在光照下使其重新聚集的能力。在光照下，α-促黑素（α-MSH）、环磷酸腺苷（cAMP）、二丁酰环磷酸腺苷（dibutyryl-cAMP）和茶碱可诱导浓度依赖性色素分散。用α-MSH获得的对数剂量-反应曲线呈S形，在0.5至2.0 ng α-MSH/ml之间有一个线性部分。在此范围内，对数剂量-反应曲线可作为黑素细胞活性生物测定的标准曲线，采用黑素细胞指数（测定I）或光度透射率测量（测定II）来定量黑素细胞反应。为防止光/暗反应的干扰，在测定过程中使用了400 - 500 nm的光（黑素细胞对此最敏感）。两种测定都显示出高精度（λI = 0.13，λII = 0.11）。测试了几种源自α-MSH的肽的黑素细胞活性。体外非洲爪蟾黑素细胞系统为研究α-MSH的作用提供了独特的特性：（1）黑素细胞系统未被其他色素细胞污染；（2）迄今为止，它是唯一适合对α-MSH受体进行光亲和标记的系统；（3）黑素细胞受体的需求与蛙属不同。
