ISSN:
1432-2013
Keywords:
Submaxillary Gland
;
Bicarbonate Secretion
;
Microperfusion
;
Acetazolamide
;
Carbachol
;
Submaxillardrüse
;
Bicarbonatsekretion
;
Mikroperfusion
;
Acetazolamid
;
Carbachol
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Bicarbonate transport in the rat submaxillary main duct has been studied by microperfusion. Bicarbonate was concentrated in the duct lumen against an electrochemical gradient and the equilibrium concentration was estimated to be 56.5 mEq/l±3.1 (S.E.M.,n=11). The secretory mechanism could not be inhibited by 6 mMolar cyanide although such concentrations caused marked inhibition of both net sodium efflux and net potassium influx. Bicarbonate secretion in the main duct was not inhibited by acetazolamide whether applied from the duct lumen or given intravenously. Similarly, the drug was without effect on bicarbonate excretion by the intact gland even when maximum excretory rates had been induced with carbachol. It was concluded that catalytic hydration of carbon dioxide to carbonic acid was not a rate-limiting step in the bicarbonate secretory process. The data did not permit a distinction to be made between a bicarbonate secretory processper se and a process of either H+ reabsorption or OH− secretion. The parasympathomimetic agent, carbachol, when given parenterally was found to increase sharply the net influx of bicarbonate into the microperfused main duct as well as to reduce net sodium efflux and net potassium influx. Previously it had been postulated that final saliva was formed in two stages. First a plasma-like primary secretion was formed at a rate depending on the degree of stimulation, and second, the primary secretion was modified in the gland duct system by reabsorptive and secretory processes whose transport rates were presumed to be independent of the degree of stimulus. It now becomes necessary to postulate that stimulation can act on electrolyte transport at both primary and secondary levels; at present, however, no data are available to show whether appreciable net water influx can ever occur at the secondary level.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00586449
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