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First published online August 3, 2006
Journal of Experimental Biology 209, 3101-3113 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02357
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Signalling pathways involved in hypertonicity- and acidification-induced activation of Na+/H+ exchange in trout hepatocytes

Khaled H. Ahmed, Bernd Pelster and Gerhard Krumschnabel*

Institut für Zoologie and Center of Molecular Biosciences, Leopold Franzens Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria


Figure 1
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  		Fig. 1. Changes in pHi (A) and in proton secretion rate (B) of trout hepatocytes upon exposing cells to hypertonicity (1.6x isosmolarity) in the presence and absence of 10 µmol l-1 cariporide. Values are means ± s.e.m. of 34-42 cells from three or four independent preparations in A and from 4-7 independent preparations in B.

 

Figure 2
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  		Fig. 2. Effect of incubation at different pHe (6.8, 7.6 and 8.2) on the hypertonicity-induced changes in pHi. Values are means ± s.e.m. of 17-42 cells from three independent preparations.

 

Figure 3
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  		Fig. 3. Changes in [Ca2+]i upon hypertonic challenge using (a) Ca2+-containing medium (control), (b) Ca2+-free medium and (c) Ca2+-free medium along with preincubation of cells with the intracellular Ca2+-chelating agent BAPTA-AM. Values are means ± s.e.m. of 21-34 cells from 3-5 independent preparations.

 

Figure 4
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  		Fig. 4. Changes in pHi upon challenging cells with hypertonicity while using (a) Ca2+-containing medium (control), (b) Ca2+-free medium and (c) Ca2+-free medium along with preincubation of cells with the intracellular Ca2+-chelating agent BAPTA-AM. Values are means ± s.e.m. of 68-95 cells from 5-10 independent preparations. Inset: pHi changes upon exposing cells to 25 µmol l-1 BAPTA-AM followed by Ca2+-free medium. Values are means ± s.e.m. of 46 cells from three independent preparations.

 

Figure 5
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  		Fig. 5. Effect of 1 and 5 µmol l-1 chelerythrine on basal pHi and on hypertonicity (hyper)-induced pHi changes (A) and the effect of 5 µmol l-1 chelerythrine on basal and hypertonic proton secretion rate (B). Values are means ± s.e.m. of 23-51 cells from three or four independent preparations in A and from four or five independent preparations in B.

 

Figure 6
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  		Fig. 6. Effect of 1 µmol l-1 H-89 on basal pHi and on hypertonicity (hyper)-induced pHi changes (A) and on basal and hypertonic proton secretion rate (B). Values are means ± s.e.m. of 27-39 cells from three or four independent preparations in A and from three independent preparations in B.

 

Figure 7
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  		Fig. 7. Effect of 5 µmol l-1 calmidazolium on basal pHi and on hypertonicity (hyper)-induced pHi changes (A) and on basal and hypertonic proton secretion rate (B). Values are means ± s.e.m. of 37-51 cells from three independent preparations in A and from four independent preparations in B.

 

Figure 8
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  		Fig. 8. Rates of proton secretion (calculated from the slope of the linear portion of the increase of pHi multiplied by ß) following hypertonic exposure. Values are expressed as percentages of the mean of the corresponding controls of each treatment.

 

Figure 9
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  		Fig. 9. pHi recovery following 30 mmol l-1 sodium-propionate-induced acidification in the absence and presence of 10 µmol l-1 cariporide (A) and in the presence of 0.5 mmol l-1 SITS or SITS + cariporide (B). Values are means ± s.e.m. of 40-79 cells from 3-5 independent preparations in A and of 44-69 cells from three independent preparations in B.

 

Figure 10
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  		Fig. 10. Effects of 5 µmol l-1 chelerythrine (A), 1 µmol l-1 H-89 (B) and 5 µmol l-1 calmidazolium (C) on basal pHi and on pHi recovery after sodium-propionate-induced acidification. Values are means ± s.e.m. of ≥40 cells from ≥4 independent preparations.

 

Figure 11
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  		Fig. 11. Rates of proton secretion (calculated from the slope of the linear portion of the increase of pHi multiplied by ß) following acid loading. Values are expressed as percentages of the mean of the corresponding controls for each treatment.

 




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