|
|
|
|
|
|
|
||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Article |
Necturus gallbladder epithelial cells bathed in 10 mM HCO3/1% CO2 display sizable basolateral membrane conductances for Cl– (GClb) and K + (GKb). Lowering the osmolality of the apical bathing solution hyperpolarized both apical and basolateral membranes and increased the K +/Cl– selectivity of the basolateral membrane. Hyperosmotic solutions had the opposite effects. Intracellular free-calcium concentration ([Ca2+]i) increased transiently during hyposmotic swelling (peak at
30 s, return to baseline within 90 s), but chelation of cell Ca2+ did not prevent the membrane hyperpolarization elicited by the hyposmotic solution. Cable analysis experiments showed that the electrical resistance of the basolateral membrane decreased during hyposmotic swelling and increased during hyperosmotic shrinkage, whereas the apical membrane resistance was unchanged in hyposmotic solution and decreased in hyperosmotic solution. We assessed changes in cell volume in the epithelium by measuring changes in the intracellular concentration of an impermeant cation (tetramethylammonium), and in isolated polarized cells measuring changes in intracellular calcein fluorescence, and observed that these epithelial cells do not undergo measurable volume regulation over 10–12 min after osmotic swelling. Depolarization of the basolateral membrane voltage (Vcs) produced a significant increase in the change in Vcs elicited by lowering basolateral solution [Cl–], whereas hyperpolarization of Vcs had the opposite effect. These results suggest that: (a) Hyposmotic swelling increases GKb and decreases G Clb. These two effects appear to be linked, i.e., the increase in G Kb produces membrane hyperpolarization, which in turn reduces G Clb. ( b) Hyperosmotic shrinkage has the opposite effects on GKb and G Clb. ( c) Cell swelling causes a transient increase in [Ca2+]i, but this response may not be necessary for the increase in GKb during cell swelling.
Key Words: transport • channel • gallbladder • cross talk • calcium
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  V. Lyall, G. L. Heck, J. A. DeSimone, and G. M. Feldman Effects of osmolarity on taste receptor cell size and function Am J Physiol Cell Physiol, October 1, 1999; 277(4): C800 - C813. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. G. Vanoye and L. Reuss Stretch-activated single K+ channels account for whole-cell currents elicited by swelling PNAS, May 25, 1999; 96(11): 6511 - 6516. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. J. Birdsey, R. D. H. Boyd, C. P. Sibley, and S. L. Greenwood Effect of hyposmotic challenge on microvillous membrane potential in isolated human placental villi Am J Physiol Regulatory Integrative Comp Physiol, May 1, 1999; 276(5): R1479 - R1488. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. G. Vanoye, A. F. Castro, T. Pourcher, L. Reuss, and G. A. Altenberg Phosphorylation of P-glycoprotein by PKA and PKC modulates swelling-activated Cl- currents Am J Physiol Cell Physiol, February 1, 1999; 276(2): C370 - C378. [Abstract] [Full Text] [PDF]
|
|
|
|
