ISSN:
1432-136X
Keywords:
Intracellular pH regulation
;
Malpighian tubules
;
V-ATPase
;
K+/H+ antiport
;
Fly, Drosophila hydei
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
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 (ΔpHlu/ΔpHo was 0.49 while ΔpHi/ΔpHo 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 μmol·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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00354085
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