Dihydropyridine receptors are primarily functional L-type calcium channels in rabbit ventricular myocytes
| Autor: | Wilbur Y.W. Lew, L. V. Hryshko, Donald M. Bers |
|---|---|
| Rok vydání: | 1991 |
| Předmět: |
medicine.medical_specialty
Dihydropyridines Physiology Heart Ventricles chemistry.chemical_element Calcium Receptors Nicotinic Internal medicine medicine Myocyte Animals L-type calcium channel Receptor Ion transporter Voltage-dependent calcium channel Ryanodine receptor Chemistry Myocardium Dihydropyridine Calcium Channel Blockers Electrophysiology Endocrinology Biophysics Calcium Channels Isradipine Rabbits Cardiology and Cardiovascular Medicine medicine.drug |
| Zdroj: | Circulation research. 69(4) |
| ISSN: | 0009-7330 |
| Popis: | We measured [3H]PN200-110 binding and patch-clamp currents in rabbit ventricular myocytes to determine if there is a disparity between the density of dihydropyridine-specific receptors and functional L-type calcium channels, as has been reported for skeletal muscle. The dihydropyridine receptor density was 74.7 +/- 4.2 fmol/mg protein (mean +/- SEM, Kd = 1.73 +/- 0.29 nM, n = 6) in ventricular homogenates and 147 +/- 6 fmol/mg protein (Kd = 1.15 +/- 0.16 nM, n = 4) in myocytes. Ventricular homogenates contained 121 +/- 9 mg protein/g wet wt (n = 7). These values were used to calculate a dihydropyridine receptor density of 12.9 dihydropyridine sites/micron2 for ventricular homogenates and 14.8 dihydropyridine sites/micron2 for myocytes. The number of functional L-type calcium channels (N) was calculated from measurements of whole-cell current (I), single-channel current (i), and open probability (po), where N = I/(i x po). We measured sodium current through calcium channels (I(ns)) to avoid calcium-induced inactivation. Whole-cell (I(ns)) and single-channel (i(ns) and po) measurements were obtained under similar ionic conditions at a test potential of -20 mV. In six cells, the peak I(ns) was approximately 105 pA/pF. The single-channel conductance was 40.8 +/- 2.6 pS (n = 12), and i(ns) at -20 mV was 1.96 pA. The mean po at -20 mV was 0.030 +/- 0.002 in 16 patches in which only a single channel was evident. The calculated density of functional L-type calcium channels was approximately 18 channels/micron2.(ABSTRACT TRUNCATED AT 250 WORDS) |
| Databáze: | OpenAIRE |
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