The Properties of Voltage-operated Ca2+-channels in Bovine Isolated Trachealis Cells
| Autor: | Roger C. Small, R.W. Foster, K.A. Green |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
Pulmonary and Respiratory Medicine
Dihydropyridines Nifedipine Population In Vitro Techniques medicine Animals Pharmacology (medical) Patch clamp General Pharmacology Toxicology and Pharmaceutics Reversal potential education education.field_of_study Chemistry Cell Membrane Pipette Conductance Muscle Smooth Depolarization 3-Pyridinecarboxylic acid 1 4-dihydro-2 6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)- Methyl ester Rats Electrophysiology Trachea Barium Trachealis muscle Biophysics Cattle Calcium Channels medicine.drug |
| Zdroj: | Pulmonary Pharmacology. 6:49-62 |
| ISSN: | 0952-0600 |
| DOI: | 10.1006/pulp.1993.1008 |
| Popis: | Summary: Freshly-dispersed bovine trachealis cells were used for recording by the patch clamp technique of whole-cell and unitary currents through Ca 2+ -channels. Whole-cell Ca 2+ -current (I Ca ) activated at -40 mV and appeared to be carried by a single type of Ca 2+ -channel. Inactivation of I Ca was increased by increasing the concentration of free Ca 2+ within the recording pipette but reduced by using Ba 2+ as the charge carrier. Steady-state inactivation studies showed that the Ca 2+ -channels were half-maximally available following a conditioning depolarization to -35 mV. A two-pulse protocol showed that I Ca induced by the step to a test potential was inversely related to I Ca induced by the step to the conditioning potential. Unitary Ba 2+ -currents were activated at a threshold of -30 mV and had a reversal potential of +41 mV. The channel carrying the unitary Ba 2+ -currents had a slope conductance of 23 pS. Steady-state inactivation studies showed that the unitary Ba 2+ -currents were half-maximally available at a holding potential of -28 mV. I Ca and unitary Ba 2+ -currents were inhibited by nifedipine (10 nM-1 μM) but augmented by Bay K 8644 (10 μM). It is concluded that the plasmalemma of bovine trachealis muscle contains a single population of voltage-dependent Ca 2+ -channels of the L-type. These channels may be subject to inactivation primarily by an increase in the concentration of free Ca 2+ on the cytosolic side of the plasmalemma and secondarily by a voltage-dependent mechanism. Overlap of the inactivation and activation curves of I Ca may allow the passage of 'window current' through the Ca 2+ -channels during sustained depolarization. |
| Databáze: | OpenAIRE |
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