Rudolph P H, Spaziani E, Wang W L
Department of Biology, University of Iowa, Iowa City 52242.
Gen Comp Endocrinol. 1992 Nov;88(2):224-34. doi: 10.1016/0016-6480(92)90254-h.
Y-organs of the xanthid crab, Menippe mercenaria, secrete ecdysteroid hormones in vitro, apparently both 3-dehydroecdysone and 25-deoxyecdysone. Studies were initiated on the biosynthetic path(s), in which cholesterol is converted to these ecdysteroids. Crabs were injected with [3H]cholesterol. Y-organs and hemolymph were removed 12 hr later and extracted directly and the extracts were analyzed by HPLC. Both polar and nonpolar sterols were surveyed. The only metabolite of cholesterol detectable in Y-organs was 7-dehydrocholesterol (identified by mass spectrometry). The total amount of 7-dehydrocholesterol and the amount that was labeled were generally greater than for cholesterol and were higher in Y-organs from de-eyestalked crabs than in those from intact crabs. Subcellular fractionation of the Y-organs showed that over 70% of total radioactivity was in cholesterol and 7-dehydrocholesterol of mitochondria and microsomes, distributed about equally between the two organellar fractions. In hemolymph, the only nonpolar sterols present were cholesterol and 7-dehydrocholesterol; the concentration ratio was 20:1. However, 7-dehydrocholesterol was not significantly labeled. Analyses of polar compounds revealed two prominent, uv-absorbing ecdysteroids which coeluted with the authentic standards, 3-dehydro-20-hydroxyecdysone and 25-deoxy-20-hydroxyecdysone (ponasterone A). The radioactivity profile showed, in addition, a third prominent peak that corresponded in retention time with 3-dehydroecdysone. These results indicate that the Y-organs in vivo form 7-dehydrocholesterol from cholesterol and convert the latter to secretion products without accumulation of other intermediates. At least two ecdysteroids are secreted and appear to be converted peripherally in this crab to their respective 20-hydroxy derivatives.
黄纹蟹（Menippe mercenaria）的Y器官在体外分泌蜕皮甾体激素，显然包括3 - 脱氢蜕皮激素和25 - 脱氧蜕皮激素。研究人员开始探究胆固醇转化为这些蜕皮甾体激素的生物合成途径。给螃蟹注射[3H]胆固醇。12小时后取出Y器官和血淋巴并直接进行提取，提取物通过高效液相色谱法进行分析。对极性和非极性甾醇都进行了检测。在Y器官中可检测到的胆固醇唯一代谢产物是7 - 脱氢胆固醇（通过质谱鉴定）。7 - 脱氢胆固醇的总量以及被标记的量通常比胆固醇的量大，并且在去眼柄螃蟹的Y器官中比完整螃蟹的Y器官中更高。Y器官的亚细胞分级分离表明，超过70%的总放射性存在于线粒体和微粒体的胆固醇和7 - 脱氢胆固醇中，在这两个细胞器部分中分布大致相等。在血淋巴中，仅存在的非极性甾醇是胆固醇和7 - 脱氢胆固醇；浓度比为20:1。然而，7 - 脱氢胆固醇没有被显著标记。极性化合物分析显示有两种突出的、具有紫外吸收的蜕皮甾体激素，它们与标准品3 - 脱氢 - 20 - 羟基蜕皮激素和25 - 脱氧 - 20 - 羟基蜕皮激素（蜕皮甾酮A）共洗脱。放射性图谱还显示，有第三个突出峰，其保留时间与3 - 脱氢蜕皮激素相对应。这些结果表明，Y器官在体内由胆固醇形成7 - 脱氢胆固醇，并将后者转化为分泌产物，而没有其他中间产物的积累。至少有两种蜕皮甾体激素被分泌出来，并且在这种螃蟹中似乎在外周被转化为它们各自的20 - 羟基衍生物。
