Molecular Mechanism of Long Distance Flight in Insects.

主要研究结果如下：脂肪动力学激素（adipokinetic hormone， AKH）的主要作用是刺激细胞外钙离子流入脂肪体细胞，通过钙依赖性蛋白激酶激活脂肪酶。因此，三酰基甘油形成二酰基甘油的速度加快，这反过来又促进脂肪体中的脂孔蛋白装载二酰基甘油。AKH诱导的低密度脂蛋白（LDLp）根据脂蛋白所载二酰基甘油的量，结合了不同数量的载脂蛋白- iii (apo-III)，从7mol /脂蛋白到14mol /脂蛋白不等，大多数ldl含有约9mol /摩尔脂蛋白。此外，证实了先前观察到的LDLp颗粒大小的异质性无疑是由于主要由AKH.3作用形成的LDLp颗粒的分子间融合所致。昆虫的血糖，海藻糖，抑制脂蛋白从脂肪体装载二酰基甘油。这种抑制发生在海藻糖的生理浓度，约60-80毫米；然而，在长途飞行开始时，海藻糖水平在前30分钟急剧下降至20 mM，该浓度不再发生抑制作用。这表明海藻糖可能具有双重功能，即在脂质转运中充当燃料和调节剂。比较了蝗虫（具有长距离飞行能力的昆虫）和蟑螂（缺乏长距离飞行能力的昆虫）。结果发现，蟑螂血淋巴缺乏载脂蛋白- iii，蟑螂脂肪体中含有极少量的二酰基甘油，仅相当于蝗虫脂肪体中二酰基甘油含量的十分之一。

The major results are summarized as follows :1. The primary action of adipokinetic hormone (AKH) is to stimulate the influx of extracellular calcium ion into the fat body cells which results in the activation of lipase via calcium-dependent protein kinase. Consequently, the formation of diacylglycerol from triacylglycerol is accelefated, which, in turn, promotes loading of diacyllgycerol by lipophporin from the fat body.2. Low density lipophorin (LDLp) induced by AKH associates a different number of apolipophorin-III (apo-III), 7moles/ lipophorin to 14 moles/lipophorin, in accordance with the amount of diacylglycerol loaded by lipophorin, and most of LDLp contain about 9 moles apo-III per each mole of lipophorin. In addition, It was confirmed that the heterogeneity in size of LDLp particles previously observed is undoubtedly due to the intermolecular fusion of LDLp particles primarily formed by the action of AKH.3. The insect blood sugar, trehalose, inhibits the loading of diacylglycerol by lipophorin from the fat body. This inhibition occurs at the physiological concentration of trehalose, about 60-80 mM ; however, at the commencement of long distance flight, the trehalose level sharply drops to 20 mM during the first 30 min, at which concentration no more inhibition takes place. This suggests that trehalose may play a dual function, i. e., serving as fuel and as a regulator in lipid transport.4. Locust (as an insect having capacity of long distance flight) and cockroach (as an insect lacking the capacity) are compared. It was found that cockroach hemolymph lacks apolipophorin-III, and that cockroach fat body contains extremely small amount of diacylglycerol, which is equivalent to only one tenth of diacylglycerol content in locust fat body.