ISSN:
1432-2013
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The ability of the main excretory duct of the rat submaxillary gland to transform a plasmalike, primary saliva into a low sodium, high potassium, final salvia, was investigated using a technique of continuous microperfusion. 1. When the duct was perfused with Ringers solution, there was a nett efflux of sodium, and a smaller nett influx of potassium, until steady-state electrolyte concentrations of 2.8 mEq/l for sodium and 135 mEq/l for potassium developed in the luminal fluid. These changes were accompanied by a small nett water efflux which declined as the steady-state concentrations were approached. The flux rates of water and electrolytes observed were sufficient to account for the changes in salivary composition observed under free-flow conditions as precursor saliva passed along the main duct to the mouth. 2. Perfusion of the duct with sodium-free solutions resulted in a nett influx of sodium to establish the same steady-state sodium concentration. Nett potassium influx also took place, although the rate of influx was reduced by more than 50% when compared with that observed during perfusion of the duct with Ringers solution. 3. Measurement of trans-epithelial potential differences associated with various intraluminal sodium and potassium concentrations demonstrated an approximately logarithmic relationship between potential difference and the intraluminal sodium concentration. The trans-epithelial potential difference was about −70 mV (lumen negative) when the duct was filled with Ringers solution, and about −11 mV (lumen negative) under steady-state (high potassium, low sodium) conditions. 4. Calculations of the electrochemical potential gradients for sodium and potassium under steady-state conditions demonstrated that both these cations underwent active transport. In addition, potassium secretion was enhanced by a favourable electrical gradient associated in some way with active sodium transport.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00362747
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