The effects of manganese and changes in internal calcium on Na-Ca exchange fluxes in the intact squid giant axon

Allen, T. Jeff A. 1990. The effects of manganese and changes in internal calcium on Na-Ca exchange fluxes in the intact squid giant axon. BBA - Biomembranes 1030 (1) , pp. 101-110. 10.1016/0005-2736(90)90244-I

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Abstract

The effects of manganese chloride were studied on Na-Ca exchange fluxes from intact squid axons. Ca uptakes and Cao-dependent sodium efflux were inhibited half-maximally by 3–7 mM MnCl2. Mn inhibition appears less during Nao-Cai exchange (half-maximal inhibition; 30 mM) than that during Cao-Nai exchange, even when both fluxes were activated with 100 mM Na. The effects of changes in [Cai2+], effected by Ca-EGTA injection or inhibition of mitochondrial Ca uptake by ruthenium red, were examined on the reverse (Cao-Nai) exchange mode. Ca-EGTA mixtures, designed to raise [Cai2+] above 2 μM, inhibited Cao-Nai exchange fluxes. Ruthenium red inhibited mitochondrial Ca buffering to effect increases in Cai in the absence of Ca chelators; it activated Nao-Cai exchange fluxes but had little effect on Cao-Nai exchange despite similar reported Km for Cai. The results reflect the difficulty in demonstrating the stimulatory effect of [Cai2+] on Cao-Nai exchange fluxes in intact axons.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Medicine
Publisher:	Elsevier
ISSN:	0005-2736
Last Modified:	15 Jan 2020 12:30
URI:	https://orca.cardiff.ac.uk/id/eprint/127188

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