Abstract |
The ability of the Ca2+-selective microelectrode to measure fast Ca2+ transients intracellularly is reviewed. In vitro, Ca microelectrodes can respond to Ca2+ injections with time to peaks as small as 40 ms. We present methods to improve the dynamic response of Ca microelectrodes and to make Ca-buffered solutions in high ionic strength. Examples of measurements of intracellular free Ca2+ [( Ca2+]i) transients in Aplysia neurons and in Limulus photoreceptors are shown. To show the validity of those measurements, simultaneous recordings of the Arsenazo III (AIII) absorbance and of the Ca-selective electrode potential were made in voltage-clamped neurons of the abdominal ganglion of Aplysia californica. Pressure injection of AIII to a concentration of 300-500 microM induced a rise in resting [Ca2+]i; injection of higher [AIII] led to buffering of [Ca2+]i transients. Both techniques responded to changes in resting [Ca2+]i in the same direction except that AIII showed an increase in absorbance in 0 [Ca2+]o. Voltage-clamp pulses transiently increased both the AIII absorbance and the Ca2+ electrode potential. Reducing or increasing the driving force for Ca2+ entry changed the magnitude of both signals in the right direction. Examples of spatial localization of [Ca2+]i increases and Ca2+ gradients within the cytoplasm were demonstrated using the Ca electrode. The use of optical techniques to measure local [Ca2+]i changes is briefly reviewed.
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Authors | S Levy, D Tillotson |
Journal | Canadian journal of physiology and pharmacology
(Can J Physiol Pharmacol)
Vol. 65
Issue 5
Pg. 904-14
(May 1987)
ISSN: 0008-4212 [Print] Canada |
PMID | 2441832
(Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Review)
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Chemical References |
- Ion Channels
- Arsenazo III
- Calcium
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Topics |
- Animals
- Arsenazo III
(pharmacology)
- Calcium
(metabolism)
- Electrochemistry
(instrumentation)
- Ion Channels
(physiology)
- Membrane Potentials
(drug effects)
- Microelectrodes
- Neurons
(physiology)
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