ISSN:
1432-1424
Keywords:
mammalian nerve
;
intracellular calcium
;
membrane-bound calcium
;
calcium buffering
;
Na/Ca exchange
;
electrical activity
;
A23187
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary A new technique for continuous monitoring of the cellular calcium was developed and used for studying the effects of external and internal Na (Na o and Na i ), external Ca (Ca o ), Ca ionophore A23187, and electrical activity on membrane-bound and intracellular Ca in mammalian nonmyelinated nerve fibers. Increasing Ca o increased both the membrane-bound and the intracellular Ca. Lowering Na o increased the membrane-bound fraction of Ca indicating that lack of Na o enhanced the capacity of the plasma membrane to bind Ca, and produced an increase of the internal Ca pool. Increasing Na i by treatment with ouabain enhanced the Ca inflow in both, the presence and absence of Na o , presumably by stimulating the Ca o /Na i exchange. The Ca ionophore A13187 produced a large and irreversible increase in the intracellular Ca without affecting the membrane-bound fraction. On the other hand, electrical activity, which is known to produce a large increase of the total Ca in squid axon, had no measurable effect on the total calcium content in our preparation. It is concluded that in mammalian nerve fibers a Ca load by exposition to Na-free solution or to A23187 produces an accumulation of Ca into the intracellular Ca stores, whereas during electrical activity the membrane-associated extrusion mechanisms are able to maintain the intracellular Ca2+ below the threshold for intracellular sequestration. Furthermore, the results indicate that the intracellular sequestration mechanisms are dependent on the internal concentration of Na.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01925792
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