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Calcium currents in the A7r5 smooth muscle-derived cell line

Marks, Theodore N
http://rave.ohiolink.edu/etdc/view?acc_num=case1054919224

Abstract Details

1990, Doctor of Philosophy, Case Western Reserve University, Biophysics and Bioengineering.
I have studied voltage dependent calcium channels in the A7r5 smooth muscle cell line using electrophysiological and biochemical techniques. A dihydropyridine (DHP) sensitive inward current resembling the 'L'-type calcium current was the dominant current in cells under voltage clamp. Inward currents were blocked by extracellular Cd2+ (IC50 ∼1 μM), and stimulated (in about half of the cells) by isoproterenol (1 μM) or forskolin (10 μM). A7r5 cells express saturable, high affinity, voltage-sensitive DHP antagonist binding sites. Suspensions of quiescent cells showed changes in resting (Ca2+) i in response to dihydropyridine agonists and increased K+. Most confluent cell monolayers showed spontaneous transient elevations in (Ca2+) i, the frequency and magnitude of which were DHP sensitive. I investigated the gating kinetics of the channels at the level of single channels and whole cell currents, in the absence and presence of DHP calcium channel agonists. Although latencies to first opening and macroscopic currents are strongly voltage dependent, analysis of amplitude histograms indicates that the primary open-closed transition is voltage-independent. This suggests that the molecular mechanisms for voltage-sensing and channel gating are di stinct, but coupled. I propose a modified Monod-Wyman-Changeux (MWC) model for channel activation, where movement of a voltage sensor is analogous to ligand binding, and the closed and open channels correspond to inactivate (T) and active (R) states. This model can account for normal gating behavior of the calcium channel, and is consistent with existing information on ion channel structure. DHP agonists lengthen single channel openings, slow deactivation kinetics, shift the activation curve to more negative potentials with an increase in slope, and reduce the latency to first opening. These effects are predicted by the MWC model, if we make the simple assumption that DHP agonists act as allosteric effectors to stabilize the open state of the channel.
Stephen Jones (Advisor)
159 p.
Calcium currents A7r5 smooth muscle derived cell line

Recommended Citations

Citations

  • Marks, T. N. (1990). Calcium currents in the A7r5 smooth muscle-derived cell line [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1054919224

    APA Style (7th edition)

  • Marks, Theodore. Calcium currents in the A7r5 smooth muscle-derived cell line. 1990. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1054919224.

    MLA Style (8th edition)

  • Marks, Theodore. "Calcium currents in the A7r5 smooth muscle-derived cell line." Doctoral dissertation, Case Western Reserve University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1054919224

    Chicago Manual of Style (17th edition)

case1054919224
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© 1990, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.