Determination of mosquito bloodmeal pH in situ by ion-selective microelectrode measurement:: implications for the regulation of malarial gametogenesis
Determination of mosquito bloodmeal pH in situ by ion-selective microelectrode measurement:: implications for the regulation of malarial gametogenesis
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DOI：
10.1017/s0031182099005946
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发表时间：
2000-06-01
期刊：
影响因子：
2.4
通讯作者：
Sinden, RE
中科院分区：
文献类型：
--
作者：
Billker, O;Miller, AJ;Sinden, RE
疟疾配子母细胞作为发育停滞的红细胞内细胞在脊椎动物宿主的外周血中循环，其仅在摄入雌性蚊子载体的血粉中时恢复发育为配子。随后的发育包括有性生殖和介导寄生虫传播给昆虫。在体外，配子发生的诱导需要温度下降和pH值从生理血液pH值（约pH 7.4）增加到约pH 8.0，或存在最近被鉴定为黄尿酸（XA）的配子细胞活化因子。然而，目前还不清楚pH值的增加或XA是否是蚊子血粉中的天然触发因素。我们在这里使用pH敏感的微电极，以确定血粉pH值在完整的蚊子。在摄入后的第一个30分钟内进行的测量，当疟疾配子发生在体内诱导，显示小的pH值从7.40（小鼠血液）增加到7.52埃及伊蚊和7.58斯氏按蚊。然而，血粉pH值显然是次优的，如果在体外诱导配子发生所需的值相比。黄尿酸被证明是扩大的pH值范围的exflagellation在体外以剂量依赖性的方式，我们已经观察到的血粉中的值，这表明在体内疟疾配子发生可以进一步调节这两个因素。
Malarial gametocytes circulate in the peripheral blood of the vertebrate host as developmentally arrested intra-erythrocytic cells, which only resume development into gametes when ingested into the bloodmeal of the female mosquito vector. The ensuing development encompasses sexual reproduction and mediates parasite transmission to the insect. In vitro the induction of gametogenesis requires a drop in temperature and either a pH increase from physiological blood pH (ca pH 7.4) to about pH 8.0, or the presence of a gametocyte-activating factor recently identified as xanthurenic acid (XA). However, it is unclear whether either the pH increase or XA act as natural triggers in the mosquito bloodmeal. We here use pH-sensitive microelectrodes to determine bloodmeal pH in intact mosquitoes. Measurements taken in the first 30 min after ingestion, when malarial gametogenesis is induced in vivo, revealed small pH increases from 7.40 (mouse blood) to 7.52 in Aedes aegypti and to 7.58 in Anopheles stephensi. However, bloodmeal pH was clearly suboptimal if compared to values required to induce gametogenesis in vitro. Xanthurenic acid is shown to extend the pH-range of exflagellation in vitro in a dose-dependent manner to values that we have observed in the bloodmeal, suggesting that in vivo malarial gametogenesis could be further regulated by both these factors.