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Ion uptake in freshwater teleosts?

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Ion uptake in freshwater teleosts?

Postby sam2400 » Wed May 05, 2010 7:37 pm

I am studying the mechanisms of aquatic living in saltwater and freshwater. Whilst looking at the uptake of Na+ and Cl- ions in the gill epithelium I came across two conflicting pieces of information.

My lecture notes say that H+ protons are pumped out of the cell which creates a negative charge inside the cell and creates a gradient that allows Na+ ions to flow in through open channels.

My textbook, Animal physiology, states that a single ATP powered pump exports H+ protons and imports Na+ ions in a single reaction.

My textbook may be a little out of date, reference below, being published in 2004. I was just wondering if anybody knows the correct mechanism of sodium import to the cells of the gill epithelium in freshwater teleosts.

Sorry if this question is a little specific, but I am having trouble getting hold of any more recent texts, and at present cannot contact the lecturer who wrote the slides.

Thanks


Animal Physiology, 2004. Hill. RW, Wyse. GA, Anderson. M
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Postby anastasianikifor » Thu Aug 26, 2010 9:15 am

From pgysiology it is well known that the concentration gradient of sodium and potassium ions across the cell membrane, determine the voltage of the potential of every cell of the body. It has been hypothesized also that the membrane of the body have powerful sodium-potassium pump that continualy pumps sodium ions to the outside and potassium ions to the inside of the cell. The pump is electromagnetic because more positive charges are pumped to the outside than to the inside (three sodium ions to the outside for two potassium ions to the inside). The theory has been developed on the measurement of the the sodium ions concentration from the outside as well as from the inside of the cell. For the measurement GLASS ELECTRODES were used. From chemistry it is known that when GLASS makes contact with aqueous media the reaction begins with an exchanging of hidronium ions (H30+) for sodium ions (Na+). Therefore, immediately, a surface layer starts to built up in which the sodium ions in the glass have been replaced by hydronium ions and for the reaction to continue, the sodium ions must diffuse through this surface layer. Thus this electromotive force is no longer proportional to the hydrogen ion concentracion because it decrease and the pH become alkaline. It follows that the measurment of the membrane potential produced/produces an "ALKALI ERROR" because the sites have become occupied by sodium ions (i.e. the quantity of the sodium ions outside is greater than inside) instead of hydrogen ions or protons. The hydrogen ions are important for life and measurement of their concentracion is crucial. It is well known also that the importance of acid-base and oxidation-reduction (REDOX) reactions in the study of water lies in the fact that the acidity and oxidative ranges in nature are those set by water and its reactions. Life has evolved between envioronments that are open (the air) and closed (single cell or internal milieu of the body) within the ranges, and values of pH and Eh (oxidation potential). Ranges outside these limit are fatal for livinf organisms.
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Re:

Postby canalon » Thu Sep 02, 2010 3:58 pm

anastasianikifor wrote:From pgysiology it is well known that the concentration gradient of sodium and potassium ions across the cell membrane, determine the voltage of the potential of every cell of the body. It has been hypothesized also that the membrane of the body have powerful sodium-potassium pump that continualy pumps sodium ions to the outside and potassium ions to the inside of the cell. [...snipped for brevity...] Life has evolved between envioronments that are open (the air) and closed (single cell or internal milieu of the body) within the ranges, and values of pH and Eh (oxidation potential). Ranges outside these limit are fatal for livinf organisms.

So you challenge the tradition. Interesting. Would you care to provide references for that? Just to be convinced?
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