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  The Ca/Ca Exchange Mode of the Na/Ca Exchanger Investigated by Photolytic Ca2+ Concentration Jumps

Haase, A., Kappl, M., Nagel, G., Wood, P. G., & Hartung, K. (2002). The Ca/Ca Exchange Mode of the Na/Ca Exchanger Investigated by Photolytic Ca2+ Concentration Jumps. Annals of the New York Academy of Sciences, 976(1), 113-116. doi:10.1111/j.1749-6632.2002.tb04728.x.

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 Creators:
Haase, Andreas1, Author           
Kappl, Michael1, Author           
Nagel, Georg1, Author           
Wood, Phillip G.1, Author           
Hartung, Klaus1, Author           
Affiliations:
1Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society, ou_2068289              

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Free keywords: DM-nitrophen; caged Ca2+; antporter
 Abstract: The Na/Ca exchanger catalyzes the countertransport of Na+ and Ca2+ as well as the self-exchange of either Na+ or Ca2+, that is, Na/Na and Ca/Ca exchange. These self-exchange modes offer a unique possibility to investigate partial reactions of the exchanger. Previously, using a combination of patch-clamp techniques and photolytic Ca2+ concentration jumps, we showed that the exchanger generates a transient current under conditions promoting Ca/Ca exchange when the Ca2+ concentration on the cytolosolic side is rapidly increased. Thus, contrary to previous suggestions, charge translocation is involved in Ca2+ translocation, although stationary Ca/Ca exchange is electroneutral. A cytosolic Ca2+ jump generates inward, not outward, current. Thus, it has been suggested that the movement of overall negative charge is correlated with the outward translocation of Ca2+. The time course of the current signal is fairly rapid: time to peak is less than 0.1 ms, and the duration is <1 ms. Thus, very fast Ca2+ concentration jumps and recording techniques are required if this signal is to be analyzed quantitatively. Photoinduced Ca2+ release from the chelator DM-nitrophen occurs with at least 38,000 s−1 (2.6 μs) and the bandwidth of the patch clamp is about 10 kHz (15 ms). To learn more about the mechanism of Ca2+ translocation, we investigated the voltage and Ca2+ dependence of the transient current. Initial experiments were performed with membrane patches excised from guinea pig cardiac myocytes. More detailed investigations were conducted with NCX1 from guinea pig expressed in Xenopus oocytes. No significant differences between either system have been observed so far. A major advantage of the oocyte system is that on the average, signal amplitudes are much larger than ones obtained with membranes from cardiac myocytes.

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Language(s): eng - English
 Dates: 2006-01-242002-11-01
 Publication Status: Published in print
 Pages: 4
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Degree: -

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Title: Annals of the New York Academy of Sciences
  Other : Ann. N.Y. Acad. Sci.
Source Genre: Journal
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Publ. Info: New York : New York Academy of Sciences
Pages: - Volume / Issue: 976 (1) Sequence Number: - Start / End Page: 113 - 116 Identifier: ISSN: 0077-8923
CoNE: https://pure.mpg.de/cone/journals/resource/954926958894_2