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Apical NAplus-Hplus exchangers in the mammalian gastrointestinal tract

100%

Kiela P. R., Xu H., Ghishan F. K.

Journal of Physiology and Pharmacology. Supplement

2006

tom 57

nr 7

51-79

The Slc9a family of nine Na+/H+ exchangers (NHE) plays a critical role in neutral sodium absorption in the mammalian intestine as well as other absorptive and secretory epithelia of digestive organs. These transport proteins mediate the electroneutral exchange of Na+ and H+ and are crucial in a variety of physiological processes, including the fine tuning of intracellular pH, cell volume control and systemic electrolyte, acid-base and fluid volume homeostasis. Here, we review the role of the Na+/H+ exchange mechanism as it relates to the physiology of organs and cells involved in nutrient absorption, and we describe physiological and molecular aspects of individual isoforms, including their structure, tissue-, and subcellular distribution, as well as their regulation by physiological stimuli at the transcriptional and post-transcriptional levels. A particular emphasis is placed on Na+/H+ exchanger isoforms expressed on the apical (brush border) membrane of the epithelial cells, and the consequences of gene-targeted mutation of individual isoforms are discussed in the context of the physiology of digestive organs. Where available, we also provide a review of pathophysiological states related to aberrant expression and/or activity of Na+/H+ exchangers within the confines of the digestive system.

The problem of water exchange by living cells in the light of mechanistic transport equations

100%

Kargol M., Suchanek G., Przestalski M., Siedlecki J., Kargol A.

Polish Journal of Environmental Studies

2005

tom 14

nr 5

Each living cell must, while performing its life functions, constantly exchange water with its surroundings. This occurs through the cell membrane. In the present paper, we have made an attempt to explain the biophysical basis of this water exchange, realized under stationary conditions, i. e. at constant cell volume. For the investigation, the mechanistic equations for membrane transport have been applied. It has been demonstrated that each living cell which subsists under stationary conditions is capable of water absorption and simultaneous water removal to its surroundings. Water absorption is osmosis-driven, while water removal is driven by the mechanical pressure difference (the turgor pressure). These are new, and very significant, research results. This stationary water exchange cannot be explained on the basis of thermodynamic transport equations.

Ograniczanie wyników

1 Journal of Physiology and Pharmacology. Supplement

1 Polish Journal of Environmental Studies

1 Ghishan F. K.

1 Kargol A.

1 Kargol M.

1 Kiela P. R.

1 Przestalski M.

1 Siedlecki J.

1 Suchanek G.

1 Xu H.

1 2006

1 2005

Wyniki wyszukiwania

Apical NAplus-Hplus exchangers in the mammalian gastrointestinal tract

The problem of water exchange by living cells in the light of mechanistic transport equations