Kawamoto F, Alejo-Blanco R, Fleck S L, Sinden R E
Department of Pure and Applied Biology, Imperial College, London, UK.
Exp Parasitol. 1991 Jan;72(1):33-42. doi: 10.1016/0014-4894(91)90118-g.
The role of ionic regulation in the induction of gametogenesis of Plasmodium berghei at 20 degrees C was investigated. A potent inhibitor of Na+/H+ exchange, amiloride, strongly inhibited exflagellation and subsequent ookinete formation induced by RPMI 1640 with 10% fetal calf serum at pH 8.0, whereas Na+ or K+ channel inhibitors, H(+)-ATPase inhibitors, and a protonophore had no significant effect. Amiloride-treated 'activated' microgametocytes synthesized DNA to levels consistent with the expected 8C, but failed to develop further. These results may suggest that an increase in intracellular pH induced by Na+/H+ exchange plays an important role in the induction of gametogenesis by cultivating at pH 8.0 and 20 degrees C. Cultivation at pH 8.0 and 37 degrees C did not induce the development, and microgametocytes remained as nonactivated forms, having the DNA content of 1.5C. By culturing at pH 7.3 and 20 degrees C, however, most of microgametocytes finished synthesis of DNA up to the 8C level, but ceased development at various stages. Additionally, exflagellation occurred in a simple medium composed of buffered saline with 10 mM glucose. Glucose was indispensable for exflagellation, presumably acting as an energy source. Exflagellation induced by this solution was also inhibited by amiloride. It is therefore suggested that the induction of microgametogenesis may be composed of two distinct mechanisms, one is a temperature-dependent DNA synthesis and the other is a pH-dependent control of developmental events leading to microgamete assembly and exflagellation.
研究了离子调节在20℃诱导伯氏疟原虫配子发生中的作用。一种有效的Na+/H+交换抑制剂氨氯地平，强烈抑制由pH 8.0的含10%胎牛血清的RPMI 1640诱导的鞭毛脱出及随后的动合子形成，而Na+或K+通道抑制剂、H(+)-ATP酶抑制剂和质子载体则无显著作用。经氨氯地平处理的“活化”小配子母细胞合成的DNA水平与预期的8C一致，但未能进一步发育。这些结果可能表明，由Na+/H+交换诱导的细胞内pH升高在pH 8.0和20℃培养诱导配子发生中起重要作用。在pH 8.0和37℃培养不诱导发育，小配子母细胞保持为未活化形式，DNA含量为1.5C。然而，通过在pH 7.3和20℃培养，大多数小配子母细胞完成了高达8C水平的DNA合成，但在不同阶段停止发育。此外，在由含10 mM葡萄糖的缓冲盐溶液组成的简单培养基中发生了鞭毛脱出。葡萄糖对于鞭毛脱出是必不可少的，大概作为能量来源。该溶液诱导的鞭毛脱出也被氨氯地平抑制。因此，提示小配子发生的诱导可能由两种不同机制组成，一种是温度依赖性DNA合成，另一种是pH依赖性对导致小配子组装和鞭毛脱出的发育事件的控制。
