Title

Calcium Transport Mechanisms in Basolateral Plasma Membrane-enriched Vesicles from Rat Parotid Gland

Document Type

Article

Publication Date

4-1-1985

Journal Title

Biochemical Journal

ISSN

0264-6021

Volume

227

Issue

1

First Page

239

Last Page

245

DOI

http://dx.doi.org/10.1042/bj2270239

Abstract

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.

Keywords

Biological transport, calcium, in vitro, parotid gland, plasma membranes, ATP, protein, sodium, rats

PubMed ID

3994684

PubMed Central® ID

PMC1144832