Dores R M, Schenk L M, Rothenberg M E
University of Denver, Department of Biological Sciences, Colorado 80208.
Gen Comp Endocrinol. 1987 Nov;68(2):322-30. doi: 10.1016/0016-6480(87)90044-x.
The effect of background adaptation on the steady-state levels of alpha-melanotropin in the pars intermedia of the larval amphibian. Ambystoma tigrinum, was investigated. Acid extracts of pars intermedia obtained from light-adapted and dark-adapted animals were analyzed by radioimmunoassay following Sephadex gel filtration chromatography, reverse-phase HPLC, and Sulfopropyl Sephadex cation-ion-exchange chromatography. For both background adaptation conditions similar results were obtained. The major form of alpha-melanotropin present in the pars intermedia has the following properties: (1) an apparent molecular mass of 1.5 kDa; (2) a net charge at pH 3.5 of +4; and (3) a retention time following reverse-phase HPLC similar to that of synthetic ACTH(1-13)amide. In dark-adapted animals a minor form of alpha-melanotropin which has a net charge of +3 at pH 3.5 was also detected. The latter form represented approximately 10% of the total alpha-melanotropin immunoreactivity in the pars intermedia of dark-adapted animals. These results strongly suggest that the predominant form of alpha-melanotropin in the pars intermedia of larval A. tigrinum is a nonacetylated ACTH(1-13)amide-like polypeptide.
研究了背景适应对幼体两栖动物美西螈中间部α-促黑素稳态水平的影响。从适应光照和适应黑暗的动物中获取中间部的酸提取物，经过葡聚糖凝胶过滤色谱、反相高效液相色谱和磺丙基葡聚糖阳离子交换色谱后，采用放射免疫分析法进行分析。对于两种背景适应条件，都得到了相似的结果。中间部存在的α-促黑素的主要形式具有以下特性：（1）表观分子量为1.5 kDa；（2）在pH 3.5时的净电荷为+4；（3）反相高效液相色谱后的保留时间与合成促肾上腺皮质激素（1-13）酰胺相似。在适应黑暗的动物中，还检测到一种次要形式的α-促黑素，其在pH 3.5时的净电荷为+3。后一种形式约占适应黑暗动物中间部总α-促黑素免疫反应性的10%。这些结果有力地表明，幼体美西螈中间部α-促黑素的主要形式是一种非乙酰化的促肾上腺皮质激素（1-13）酰胺样多肽。
