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.
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Research Article| April 01 1985
Calcium transport mechanisms in basolateral plasma membrane-enriched vesicles from rat parotid gland
Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1985 London: The Biochemical Society
Biochem J (1985) 227 (1): 239–245.
T Takuma, B L Kuyatt, B J Baum; Calcium transport mechanisms in basolateral plasma membrane-enriched vesicles from rat parotid gland. Biochem J 1 April 1985; 227 (1): 239–245. doi: https://doi.org/10.1042/bj2270239
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