Gurney, Alison M. and Nerbonne, Jeanne M. and Lester, Henry A. (1985) Photoinduced Removal of Nifedipine Reveals Mechanisms of Calcium Antagonist Action on Single Heart Cells. Journal of General Physiology, 86 (3). pp. 353-379. ISSN 0022-1295 http://resolver.caltech.edu/CaltechAUTHORS:20120629-070830645
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The currents through voltage-activated calcium channels in heart cell membranes are suppressed by dihydropyridine calcium antagonists such as nifedipine. Nifedipine is photolabile, and the reduction of current amplitude by this drug can be reversed within a few milliseconds after a 1-ms light flash. The blockade by nifedipine and its removal by flashes were studied in isolated myocytes from neonatal rat heart using the whole-cell clamp method. The results suggest that nifedipine interacts with closed, open, and inactivated calcium channels. It is likely that at the normal resting potential of cardiac cells, the suppression of current amplitude arises because nifedipine binds to and stabilizes channels in the resting, closed state. Inhibition is enhanced at depolarized membrane potentials, where interaction with inactivated channels may also become important. Additional block of open channels is suggested when currents are carried by Ba^(2+) but is not indicated with Ca^(2+) currents. Numerical simulations reproduce the experimental observations with molecular dissociation constants on the order of 10^(-7) M for closed and open channels and 10^(-8) M for inactivated channels.
|Additional Information:||© 1985 The Rockefeller University Press. Original version received 4 December 1984 and accepted version received 7 May 1985. This work was supported by the Del E. Webb Foundation (fellowship to A.M.G.), Fulbright Hayes (travel grant to A.M.G.), the Los Angeles Affiliate of the American Heart Association (fellowships to A.M.G. and J.M.N.), the National Office of the American Heart Association (established investigatorship to J.M.N.), and the National Institutes of Health (grant GM-29836).|
|Official Citation:||Photoinduced removal of nifedipine reveals mechanisms of calcium antagonist action on single heart cells. A M Gurney, J M Nerbonne, and H A Lester 86:353-379. doi:10.1085/jgp.86.3.353|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||02 Jul 2012 16:33|
|Last Modified:||26 Dec 2012 15:26|
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