Atella G C, Gondim C, Masuda H
Departamento de Bioquímica Médica, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Arch Insect Biochem Physiol. 1995;30(2-3):337-50. doi: 10.1002/arch.940300404.
32P-Labelled midguts (32P-midguts) of Rhodnius prolixus females were incubated in the presence of nonradioactive purified lipophorin and the release of radioactivity to the medium was analysed. The radioactivity found in the medium was associated with lipophorin phospholipids. When the 32P-midguts were incubated in the absence of lipophorin, no 32P-phospholipids were found in the medium. Comparative analysis by thin-layer chromatography of 32P-phospholipids derived from metabolically labelled 32P-midgut or lipophorin particles after incubation with 32P-midgut showed some differences, revealing a possible selectivity in the process of phospholipids transfer. The transfer of phospholipids to lipophorin was linear with time up to 45 min, was saturable with respect to the concentration of lipophorin, and was half-maximal at about 5 mg/ml. The binding of 32P-lipophorin to the midgut at 0 degrees C reached the equilibrium at about 1 h of incubation. The binding of 32P-lipophorin was inhibited by an excess of nonradioactive lipophorin, which suggests a specific receptor for lipophorin. The capacity of midguts and fat bodies to transfer phospholipids to lipophorin varied during the days following the meal. When lipophorin enzymatically depleted of phospholipids by treatment with phospholipase A2 was incubated with 32P-midguts, the same amount of phospholipids was transferred, indicating a net gain of phospholipids by the particle.
将含有32P标记的雌性红带锥蝽中肠（32P - 中肠）与非放射性的纯化脂载蛋白一起孵育，并分析向培养基中释放的放射性。培养基中发现的放射性与脂载蛋白磷脂相关。当在没有脂载蛋白的情况下孵育32P - 中肠时，培养基中未发现32P - 磷脂。对与32P - 中肠孵育后从代谢标记的32P - 中肠或脂载蛋白颗粒衍生的32P - 磷脂进行薄层色谱比较分析，发现了一些差异，揭示了磷脂转移过程中可能存在的选择性。磷脂向脂载蛋白的转移在长达45分钟内随时间呈线性，相对于脂载蛋白浓度是可饱和的，在约5mg/ml时达到半数最大转移量。32P - 脂载蛋白在0℃下与中肠的结合在孵育约1小时后达到平衡。过量的非放射性脂载蛋白可抑制32P - 脂载蛋白的结合，这表明存在脂载蛋白的特异性受体。在进食后的几天里，中肠和脂肪体向脂载蛋白转移磷脂的能力有所不同。当用磷脂酶A2处理使脂载蛋白的磷脂酶解后与32P - 中肠孵育时，转移的磷脂量相同，表明该颗粒净获得了磷脂。
