果蝇幼虫马氏管中质膜V-ATP酶对细胞内pH的调节

Intracellular pH regulation by the plasma membrane V-ATPase in Malpighian tubules of Drosophila larvae.

作者信息

Bertram G, Wessing A

机构信息

Institut für Allgemeine und Spezielle Zoologie, Justus-Liebig-Universität, Giessen, Germany.

出版信息

J Comp Physiol B. 1994;164(3):238-46. doi: 10.1007/BF00354085.

DOI:10.1007/BF00354085

PMID:8089311

Abstract

The functional significance of the apical vacuolar-type proton pump (V-ATPase) in Drosophila Malpighian tubules was studied by measuring the intracellular pH (pHi) and luminal pH (pHlu) with double-barrelled pH-microelectrodes in proximal segments of the larval anterior tubule immersed in nominally bicarbonate-free solutions (pHo 6.9). In proximal segments both pHi (7.43 +/- 0.20) and pHlu (7.10 +/- 0.24)) were significantly lower than in distal segments (pHi 7.70 +/- 0.29, pHlu 8.09 +/- 0.15). Steady-state pHi of proximal segments was much less sensitive to changes in pHo than pH of the luminal fluid (delta pHlu/delta pHo was 0.49 while delta pHi/delta pHo was 0.18; pHo 6.50-7.20). Re-alkaliniziation from an NH4Cl-induced intracellular acid load (initial pHi recovery rate 0.55 +/- 0.34 pH.min-1) was nearly totally inhibited by 1 mmol.l-1 KCN (96% inhibition) and to a large degree (79%) by 1 mumol.l-1 bafilomycin A1. In contrast, both vanadate (1 mmol.l-1) and amiloride (1 mmol.l-1) inhibited pHi recovery by 38% and 33%, respectively. Unlike amiloride, removal of Na+ from the bathing saline had no effect on pHi recovery, indicating that a Na+/H+ exchange is not significantly involved in pHi regulation. Instead pHi regulation apparently depended largely on the availability of ATP and on the activity of the bafilomycin-sensitive proton pump.

摘要

通过使用双管pH微电极，在浸泡于名义上无碳酸氢盐溶液（pHo 6.9）中的幼虫前肾小管近端段中测量细胞内pH（pHi）和管腔pH（pHlu），研究了果蝇马氏管中顶端液泡型质子泵（V-ATP酶）的功能意义。在近端段，pHi（7.43±0.20）和pHlu（7.10±0.24）均显著低于远端段（pHi 7.70±0.29，pHlu 8.09±0.15）。近端段的稳态pHi对pHo变化的敏感性远低于管腔液的pH（ΔpHlu/ΔpHo为0.49，而ΔpHi/ΔpHo为0.18；pHo 6.50 - 7.20）。从氯化铵诱导的细胞内酸负荷中重新碱化（初始pHi恢复率0.55±0.34 pH·min⁻¹）几乎完全被1 mmol·l⁻¹ KCN抑制（96%抑制），并在很大程度上（79%）被1 μmol·l⁻¹巴弗洛霉素A1抑制。相比之下，钒酸盐（1 mmol·l⁻¹）和氨氯吡脒（1 mmol·l⁻¹）分别抑制pHi恢复38%和33%。与氨氯吡脒不同，从浴盐中去除Na⁺对pHi恢复没有影响，表明Na⁺/H⁺交换在pHi调节中不显著。相反，pHi调节显然很大程度上取决于ATP的可用性和巴弗洛霉素敏感质子泵的活性。