Involvement of carboxyl groups in the divalent cation permeability of rat parotid gland basolateral plasma membrane

1993 ◽  
Vol 126 (2) ◽  
pp. 143-150 ◽  
Author(s):  
Timothy Lockwich ◽  
Lawrence M. Mertz ◽  
Indu S. Ambudkar
Keyword(s):  
Plasma Membrane ◽  
Parotid Gland ◽  
Divalent Cation ◽  
Carboxyl Groups ◽  
Cation Permeability ◽  
Rat Parotid Gland ◽  
Basolateral Plasma Membrane ◽  
Rat Parotid

scholarly journals Calcium transport mechanisms in basolateral plasma membrane-enriched vesicles from rat parotid gland

1985 ◽  
Vol 227 (1) ◽  
pp. 239-245 ◽  
Author(s):  
T Takuma ◽  
B L Kuyatt ◽  
B J Baum
Keyword(s):  
Plasma Membrane ◽  
Parotid Gland ◽  
Gradient Centrifugation ◽  
Membrane Vesicles ◽  
Transport Systems ◽  
Transport Mechanisms ◽  
Plasma Membrane Vesicles ◽  
Rat Parotid Gland ◽  
Basolateral Plasma Membrane ◽  
Rat Parotid

Ca2+ transport was studied by using basolateral plasma membrane vesicles from rat parotid gland prepared by a Percoll gradient centrifugation method. In these membrane vesicles, there were two Ca2+ transport systems; Na+/Ca2+ exchange and ATP-dependent Ca2+ transport. An outwardly directed Na+ gradient increased Ca2+ uptake. Ca2+ efflux from Ca2+-preloaded vesicles was stimulated by an inwardly directed Na+ gradient. However, Na+/Ca2+ exchange did not show any ‘uphill’ transport of Ca2+ against its own gradient. ATP-dependent Ca2+ transport exhibited ‘uphill’ transport. An inwardly directed Na+ gradient also decreased Ca2+ accumulation by ATP-dependent Ca2+ uptake. The inhibition of Ca2+ accumulation was proportional to the external Na+ level. Na+/Ca2+ exchange was inhibited by monensin, tetracaine and chlorpromazine, whereas ATP-dependent Ca2+ transport was inhibited by orthovanadate, tetracaine and chlorpromazine. Oligomycin had no effect on either system. These results suggest that in the parotid gland cellular free Ca2+ is extruded mainly by an ATP-dependent Ca2+ transport system, and Na+/Ca2+ exchange may modify the efficacy of that system.

scholarly journals Plasma membrane of the rat parotid gland: preparation and partial characterization of a fraction containing the secretory surface.

1982 ◽  
Vol 95 (1) ◽  
pp. 8-19 ◽  
Author(s):  
P Arvan ◽  
J D Castle
Keyword(s):  
Plasma Membrane ◽  
Parotid Gland ◽  
Membrane Fraction ◽  
Adenosine Triphosphatase ◽  
Plasma Membranes ◽  
Junctional Complex ◽  
Salivary Gland Cell ◽  
Plasma Membrane Fraction ◽  
Rat Parotid Gland ◽  
Rat Parotid

A plasma membrane fraction from the rat parotid gland has been prepared by a procedure which selectively enriches for large membrane sheets. This fraction appears to have preserved several ultrastructural features of the acinar cell surface observed in situ. Regions of membrane resembling the acinar luminal border appear as compartments containing microvillar invaginations, bounded by elements of the junctional complex, and from which basolateral membranes extend beyond the junctional complex either to contact other apical compartments or to terminate as free ends. Several additional morphological features of the apical compartments suggest that they are primarily derived from the surface of acinar cells, rather than from the minority of other salivary gland cell types. Enzymatic activities characteristically associated with other cellular organelles are found at only low levels in the plasma membrane fraction. The fraction is highly enriched in two enzyme activities--K+ -dependent p-nitrophenyl phosphatase (K+ -NPPase, shown to be Na+/K+ adenosine triphosphatase; 20-fold) and gamma-glutamyl transpeptidase (GGTPase; 26-fold)--both known to mark plasma membranes in other tissues. These activities exhibit different patterns of recovery during fractionation, suggesting their distinct distributions among parotid cellular membranes. Secretion granule membranes also exhibit GGTPase, but no detectable K+ -NPPase. Since Na+/K+ adenosine triphosphatase and GGTPase, respectively, mark the basolateral and apical cellular surfaces in other epithelia, we hypothesize that these two enzymes mark distinct domains in the parotid plasmalemma, and that GGTPase, as the putative apical marker, may signify a compositional overlap between the two types of membranes which fuse during exocytosis.

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