Recovery of cell volume and electrolytes of A6 cells after re-establishing isotonicity following hypotonic stress.
Cellular element concentrations and dry weight contents in A6 cells were determined using electron microprobe analysis to establish whether these cells exhibit a regulatory volume increase (post-RVD-RVI) when re-establishing isotonicity following a hypotonically induced regulatory volume decrease (RVD). Hypotonic stress was induced by reducing basolateral [NaCl], and hence, osmolarity fell from 260 to 140 mosmol/l. The alterations in cell volume after re-establishing isotonicity, calculated from the cellular dry weight changes, indicate within the first 2 min cell shrinkage from 120 to 76% of control, compatible with almost ideal osmometric behaviour of A6 cells, and thereafter a post-RVD-RVI to 94%. The cellular uptake of osmolytes necessary to explain the post-RVD-RVI could be accounted for solely by a gain in cellular K and Cl. The involvement of a Na-K-2Cl cotransporter in most of the KCl uptake seems plausible since basolateral bumetanide blocked KCl uptake and post-RVD-RVI. The net uptake of cations (K uptake of 185.2, Na loss of 8.2 mmol/kg dry wt) during the isotonic period exceeded the Cl uptake by 38.2 mmol/kg dry wt, suggesting the uptake of another anion and/or the alteration of cellular buffer capacity. The relatively low Na concentration maintained during the isotonic period (13.3 vs. 20.4 mmol/kg wet wt under control conditions) might favour electrolyte uptake via the Na-K-2Cl cotransporter.
Grosse
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Physiologisches Institut, Pettenkoferstrasse 12, 80336 Munich, Germany.
Heid
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I
Oztürk
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I
Borgmann
S
S
Beck
F X
FX
Dörge
A
A
D000818:Animals; D002461:Cell Line, Transformed; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D004573:Electrolytes / Q000032:analysis* / Q000378:metabolism; D007038:Hypotonic Solutions / Q000032:analysis* / Q000378:metabolism; D007552:Isotonic Solutions / Q000032:analysis* / Q000378:metabolism; D009994:Osmolar Concentration; D013312:Stress, Physiological / Q000378:metabolism*; D014982:Xenopus laevis
D004573:Electrolytes; D007038:Hypotonic Solutions; D007552:Isotonic Solutions