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The CaATPase activity of rat-incisor odontoblast vesicles

Highsmith, S., Bloebaum, P., Smith, D. and Claydon, N. 2004. The CaATPase activity of rat-incisor odontoblast vesicles. Archives of Oral Biology 32 (10) , pp. 745-749. 10.1016/0003-9969(87)90120-8

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Abstract

An homogenate of rat incisor odontoblasts had Ca2+ and Mg2+ ATPase activity and suitable storage conditions kept it stable for several days. Over 90 per cent of the activity was retained in a vesicle-rich microsomal fraction that removed about 85 per cent of the total material from the homogenate. This fraction was further characterized: the resolved Ca2+-activated ATPase activity, above the basal MgATPase activity, was 0.30 μmol P1/min-mg total protein, and 50 per cent activated at free [Ca2+] equal 0.8 μM. This calcium dependency is consistent with an intracellular Ca2+-regulated enzymatic activity. The calcium ionophore, A23187, had no measurable effect on the CaATPase activity, which suggests that the odontoblast vesicles do not concentrate Ca2+ in a lipid bilayer compartment. Direct measurement of the uptake of 45Ca2+ by the filtration method and parallel measurements of CaATPase activity on the same preparations under identical conditions indicated that the odontoblastderived vesicles have a coupling ratio of 0.024 Ca2+/ATP. This low coupling ratio and the lack of detectable compartmentalization of calcium indicate that the CaATPase activity of the odontoblast microsomes is not associated with a calcium pump. The [Ca2+] dependence of the activity suggests the CaATPase is under intracellular Ca2+ control, but its function is unknown.

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Dentistry
Publisher: Elsevier
ISSN: 0003-9969
Last Modified: 04 Jun 2020 18:20
URI: http://orca-mwe.cf.ac.uk/id/eprint/118052

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