Calcium channel selectivity for divalent and monovalent cations. Voltage and concentration dependence of single channel current in ventricular heart cells.
Key result
In guinea pig ventricular heart cells, calcium channels show higher permeability for Ca2+ over other cations based on reversal potential, but higher permeability ions have lower ion transfer rates.
Population
Isolated ventricular heart cells of guinea pigs
Design
Preclinical
Authors
Discussion
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Member takes
Implication
Does not guide clinical calcium channel therapies; leaves open translation of pore-affinity mechanisms to human ventricular myocytes.
Key Points
- This research aims to understand ion permeation and selectivity through calcium channels in ventricular heart cells.
- Used single channel and whole cell recordings from isolated guinea pig ventricular heart cells.
- Measured unitary current amplitude and reversal potential (Erev) for various divalent and monovalent ions.
- Analyzed the permeability sequences and conductance rates of different ions through calcium channels.
- Divalent ion permeability sequence: Ca2+ > Sr2+ > Ba2+, with Mg2+ not measurably permeant.
- Monovalent ion permeability sequence: Li+ > Na+ > K+ > Cs+, significantly less permeant than divalent ions.
- Channel conductance estimates indicate that higher Erev ion permeability corresponds to lower transfer rates, contradicting initial expectations.
Structured PICO
P
Population
Isolated ventricular heart cells of guinea pigs
E
Exposure
Exposure to various divalent (Ca2+, Sr2+, Ba2+, Mg2+) and monovalent (Li+, Na+, K+, Cs+) cations
O
Outcome
Ion permeation measured by unitary current amplitude and reversal potential (Erev)surrogate
Calcium channel selectivity in ventricular cells is driven by ion affinity to binding sites in the pore, where higher permeability (by Erev) is associated with lower ion transfer rates.
Cite This Study
Hess et al. (1986) studied this question. Ion permeation of divalent and monovalent cations was evaluated on Permeability to various divalent and monovalent cations measured by unitary current amplitude or reversal potential. In guinea pig ventricular heart cells, calcium channels show higher permeability for Ca2+ over other cations based on reversal potential, but higher permeability ions have lower ion transfer rates.