News Reader.info

ABSTRACT A PLASMALEMMAL Na+–Ca2+ exchange mechanism1,2 is an important electrogenic determinant of contractility in cardiac cells3–5. As in other cell types6–8, calcium influx by

Na+–Ca2+" exchange is secondarily activated by cytoplasmic calcium4 and probably ATP9, but these modulatory mechanisms are either absent or altered in isolated cardiac sarcolemmal

vesicles5,12. Involvement of a calcium-dependent protein kinase in exchange regulation has been suggested7,10 but not verified5,11. Here I describe measurements of outward Na+–Ca2+ exchange

current, corresponding to calcium influx, in giant excised sarcolemmal Patches11 from guinea pig myocytes. The exchange current is stimulated by both calcium and Mg–ATP from the cytoplasmic

face, evidently through separate mechanisms. Activation by cytoplasmic calcium takes place within seconds, is reversible, and does not require ATP. Stimulation by Mg–ATP reverses only slowly

over > 10 min, or not at all. Unexpectedly, a substantial decrease in exchange current occurs during activation by cytoplasmic sodium, which seems to reflect an inactivation process

rather than ion concentration changes or a 'first pass' exchange cycle. This apparent inactivation, and the modulations by cytoplasmic calcium and Mg–ATP, are all abolished by

brief treatment of the cytoplasmic surface with chymotrypsin, leaving the exchanger in a maintained state of high activity. Therefore, limited proteolysis deregulates Na+–Ca2+ exchange and

could contribute to the loss of secondary regulation of the exchange in isolated sarcolemmal vesicles. Access through your institution Buy or subscribe This is a preview of subscription

content, access via your institution ACCESS OPTIONS Access through your institution Subscribe to this journal Receive 51 print issues and online access $199.00 per year only $3.90 per issue

Learn more Buy this article * Purchase on SpringerLink * Instant access to full article PDF Buy now Prices may be subject to local taxes which are calculated during checkout ADDITIONAL

ACCESS OPTIONS: * Log in * Learn about institutional subscriptions * Read our FAQs * Contact customer support SIMILAR CONTENT BEING VIEWED BY OTHERS SARCOPLASMIC RETICULAR CA2+-ATPASE

INHIBITION PARADOXICALLY UPREGULATES MURINE SKELETAL MUSCLE NAV1.4 FUNCTION Article Open access 02 February 2021 GATING THE PORE OF THE CALCIUM-ACTIVATED CHLORIDE CHANNEL TMEM16A Article

Open access 04 February 2021 THE MOLECULAR TRANSITION THAT CONFERS VOLTAGE DEPENDENCE TO MUSCLE CONTRACTION Article Open access 24 May 2025 REFERENCES * Reuter, H. & Seitz, N. _J.

Physiol._ 195, 451–470 (1968). Article  CAS  Google Scholar  * Allen, T. J. A., Noble, D. & Reuter, H. (eds) _Sodium-Calcium Exchange_ (Oxford University Press, 1989). * Hilgemann, D. W.

& Noble, D. _Proc. R. Soc._ B 230, 163–205 (1987). ADS  CAS  Google Scholar  * Kimura, J., Miyame, S. & Noma, A. _J. Physiol._ 384, 199–222 (1987). Article  CAS  Google Scholar  *

Reeves, J. P. in _Intracellular Calcium Regulation_ (ed. Bronner F.) 305–347 (Liss, New York, 1990). Google Scholar  * Baker, P. & McNaughton, P. A. _J. Physiol._ 259, 103–144 (1976).

Article  CAS  Google Scholar  * DiPolo, R. & Beaugé, L. _Biochlm. biophys. Acta_ 947, 549–569 (1988). CAS  Google Scholar  * Rasgado-Flores, H., Santiago, M. & Blaustein, M. P. _J.

gen. Physiol._ 93, 1219–1242 (1989). Article  CAS  Google Scholar  * Haworth, R. A., Gonknur, A. B., Hunter, D. R., Hegge, J. O. & Berkoff, H. A. _Circulation. Res._ 60, 586–594 (1987).

Article  CAS  Google Scholar  * Caroni, P. & Carafoli, E. _Eur. J. Biochem._ 132, 451–460 (1983). Article  CAS  Google Scholar  * Hilgemann, D. W. _Pflügers Arch. ges Physiol._ 415,

247–249 (1989). Article  CAS  Google Scholar  * Hilgemann, D. W. _Prog. Biophys. molec. Biol._ 51, 1–45 (1988). Article  CAS  Google Scholar  * Hamill, O. P., Marty, A., Neher, E., Sakmann,

B. & Sigworth, F. J. _Pflügers Arch. ges Physiol._ 391, 85–100 (1981). Article  CAS  Google Scholar  * Allen, T. J. A. & Baker, P. F. _J. Physiol._ 378, 53–76 (1986). Article  CAS 

Google Scholar  * Cervetto, L., Lagnado, L., Perry, R. J., Robinson, D. W. & McNaughton, P. A. _Nature_ 337, 740–743 (1989). Article  ADS  CAS  Google Scholar  * DiPolo, R., _J. gen.

Physiol._ 73, 91–113 (1977). Article  Google Scholar  * Philipson, K. D. & Nishimoto, A. Y. _Am. J. Physiol._ 243, 191–195 (1982). Article  Google Scholar  * Philipson, K. D., Longoni,

S. & Ward, R. _Biochim. biophys. Acta_ 945, 298–306 (1988). Article  CAS  Google Scholar  Download references AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Department of Physiology,

University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, 75235, USA Donald W. Hilgemann Authors * Donald W. Hilgemann View author publications You can also search for this

author inPubMed Google Scholar RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Hilgemann, D. Regulation and deregulation of cardiac Na+–Ca2+ exchange in

giant excised sarcolemmal membrane patches. _Nature_ 344, 242–245 (1990). https://doi.org/10.1038/344242a0 Download citation * Received: 31 July 1989 * Accepted: 12 January 1990 * Issue

Date: 15 March 1990 * DOI: https://doi.org/10.1038/344242a0 SHARE THIS ARTICLE Anyone you share the following link with will be able to read this content: Get shareable link Sorry, a

shareable link is not currently available for this article. Copy to clipboard Provided by the Springer Nature SharedIt content-sharing initiative