Until recently, intracellular free calcium has been amenable to measurement and investigation only in cells large enough to permit either microinjection of a suitable Ca sensor such as aequorin or arsenazo III or insertion of a Ca-sensitive microelectrode1,2. This constraint on cell size was removed by the development of the fluorescent Ca2+-sensitive dye Quin-2 and its acetoxymethyl ester, which can be introduced into a wide range of cell types3,4. A major requirement of any intracellular Ca2+ indicator is that it should not disturb intracellular Ca2+ homeostasis and Quin-2 is generally considered to be satisfactory in this respect5. We now report that injection of Quin-2 into squid (Loligo forbesi) axons can almost completely abolish one component of Ca2+ entry—intracellular Na+ (Nai)-dependent Ca2+ inflow, which occurs via Na/Ca exchange6. Mixtures of Ca and Quin-2 that buffer an ionized Ca2+ at close to physiological concentrations also block Nai-dependent Ca2+ influx but these same mixtures fail to block the extracellular Na+ (NaO)-dependent extrusion of Ca2+, showing that Quin-2 acts specifically on Ca2+ inflow.
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Baker, P. F. Prog. Biophys. molec. Biol. 24, 177–223 (1972).
Baker, P. F. & Dipolo, R. Curr. Topics Membranes Transp. 22, 195–247 (1984).
Tsien, R. Y. Biochemistry 19, 2396–2404 (1980).
Tsien, R. Y. Nature 290, 527–528 (1981).
Tsien, R. Y., Pozzan, T. & Rink, T. J. J. Cell Biol. 94, 325–334 (1982).
Baker, P. F., Blaustein, M. P., Hodgkin, A. L. & Steinhardt, R. A. J. Physiol., Lond. 200, 431–458 (1969).
Baker, P. F. in Calcium and Cell Function (ed. Cuthbert, A. W.) (Macmillan, London, 1970).
Baker, P. F. & McNaughton, P. A. J. Physiol., Lond. 259, 103–144 (1976).
Simons, T. J. B. J. Membrane Biol. 84, 61–77 (1985).
Arslan, P., Di Virgilio, F., Beltrame, M., Tsien, R. Y. & Pozzan, T. J. biol. Chem. (in the press).
Dipolo, R. J. gen. Physiol. 73, 91–113 (1979).
Alien, T. J. A. & Baker, P. F. J. Physiol., Lond. 345, 80p (1983).
About this article
Cite this article
Allen, T., Baker, P. Intracellular Ca indicator Quin-2 inhibits Ca2+ inflow via Nai/Cao exchange in squid axon. Nature 315, 755–756 (1985). https://doi.org/10.1038/315755a0
Progress in Neurobiology (2007)
Physiological Reviews (2006)
Ascending aortic stenosis selectively increases action potential-induced Ca2+influx in epicardial myocytes of the rat left ventricle
Experimental Physiology (2005)
Physiological Reviews (1999)
Relationship between transient outward K+current and Ca2+influx in rat cardiac myocytes of endo- and epicardial origin
The Journal of Physiology (1999)