Metabolic changes in Giardia intestinalis during differentiation
Metabolic changes in Giardia intestinalis during differentiation
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DOI：
10.2307/3284474
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发表时间：
1998-04-01
影响因子：
1.3
通讯作者：
Jarroll, EL
中科院分区：
文献类型：
--
作者：
Paget, TA;Macechko, PT;Jarroll, EL
贾第鞭毛虫包囊的吸氧率和甲硝唑（MTZ）敏感性比滋养体大大降低。因此，该项目的目的是评估在成囊过程中何时发生这些现象。在成囊的前 5 小时内，摄氧率大约翻倍（从 4.9 到 8.3 mu M O-2 min(-1) 10(-6) 细胞）。此增加随后在 12 小时内显着降低至 2.3 mu M O-2 min(-1) 10(-6)。 50小时后进入包囊站。摄氧量为0.7 μM O-2 min(-1) 10(-6) 细胞。葡萄糖刺激滋养体中 89% 的氧气摄取，但在形成包囊 12 小时后并没有明显刺激细胞的氧气摄取。与非成囊细胞相比，成囊细胞的脱氧-D-葡萄糖摄取下降了一个数量级以上。相比之下，无论细胞是否成囊，天冬氨酸的摄取都保持相对恒定。这表明寄生虫在包囊形成过程中转运葡萄糖的能力发生了变化：在进入包囊40小时后，没有观察到寄生虫转运天冬氨酸的能力发生类似的变化。 MTZ 抑制滋养体中 77% 的摄氧量，但在滋养体转移至包囊培养基后 8 小时，没有检测到对摄氧量的抑制。我们认为，这种对 MTZ 的抗性可能是由于远离丙酮酸铁氧还蛋白氧化还原酶途径的代谢通量的变化所致。在诱导排泄后的 30 分钟内，非诱导包囊的耗氧量呈指数增加。同样，MTZ 敏感性在诱导排泄后 15 分钟内恢复，并在排泄 30 分钟后完全恢复敏感性。
The oxygen uptake rate and metronidazole (MTZ) sensitivity in Giardia spp, cysts is greatly reduced from that in trophozoites. Thus, this project was undertaken to assess when in the encystation process these phenomena occur. Oxygen uptake rates approximately doubled (from similar to 4.9 to 8.3 mu M O-2 min(-1) 10(-6) cells) during the first 5 hr into encystation. This increase was followed by a marked decrease to 2.3 mu M O-2 min(-1) 10(-6) by 12 hr. By 50 hr into encystation. oxygen uptake was 0.7 mu M O-2 min(-1) 10(-6) cells. Glucose stimulated oxygen uptake by 89% in trophozoites but did not demonstrably stimulate oxygen uptake in cells after 12 hr into encystment. Deoxy-D-glucose uptake dropped by more than an order of magnitude in encysting cells compared to nonencysting cells. In contrast, aspartate uptake remained relatively constant regardless of whether cells were encysting or not. This suggests that there is a change in the parasite's ability to transport glucose during cyst formation: a similar change in the parasite's ability to transport aspartate was not observed after 40 hr into encystation. MTZ inhibited oxygen uptake by 77% in trophozoites, but there was no detectable inhibition of oxygen uptake 8 hr after trophozoites were transferred to encystation medium. We propose that this resistance to MTZ may be due to a change in metabolic flux away from the pyruvate ferredoxin oxidoreductase pathway. Oxygen uptake by noninduced cysts increased exponentially during the 30 min following the induction of excystation. Likewise, MTZ sensitivity returned within 15 min after the induction of excystation, and by 30 min into excystation full sensitivity had returned.