Slow inward current in single cells isolated from adult human ventricles
| Autor: | Jean-Pierre Benitah, M.-C. D'agrosa, Carmen Delgado, J. P. Da Ponte, P. Bailly, Paco Lorente |
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| Rok vydání: | 1992 |
| Předmět: |
Male
medicine.medical_specialty Potassium Channels Heart Diseases Physiology Cations Divalent Heart Ventricles Clinical Biochemistry chemistry.chemical_element Cesium Calcium In Vitro Techniques Membrane Potentials Physiology (medical) medicine Myocyte Humans Diltiazem 4-Aminopyridine Reversal potential Aged Aged 80 and over Cardiac transient outward potassium current Myocardium Time constant Adrenergic beta-Agonists Middle Aged Calcium Channel Blockers Surgery Electrophysiology chemistry Biophysics Female Current (fluid) medicine.drug |
| Zdroj: | Pflugers Archiv : European journal of physiology. 421(2-3) |
| ISSN: | 0031-6768 |
| Popis: | Characteristics of the slow inward current (Isi) in human ventricular myocytes isolated from septal specimens obtained in patients undergoing corrective cardiac surgery were studied using the whole-cell clamp method. A first series of experiments was performed under normal standard superfusion. Clamping from -60 mV evoked an inward current with a threshold at about -35 mV, a maximum around +10 mV and an apparent reversal potential at about +55 mV. No overlapping transient or background outward currents were detected in the -60 to +30 mV potential range, but time-dependent and steady-state outward currents were elicited at potentials above +30 mV. An overlap of steady-state activation and inactivation curves was present between -30 and +10 mV and a slight relief from inactivation was observed for voltages positive to +10 mV. The time course of inactivation consisted of fast and slow phases with time constants differing by a factor of eight. Slow time constants of inactivation were shorter at potentials that elicited larger Isi, and longer at potentials inducing smaller Isi. Recovery from inactivation evolved slowly with 100% reactivation occurring in about 4000 ms. Switching the holding potential from -60 to -40 mV led to a reversible decline of Isi without any change of the decay time constants. Isi was significantly increased by 0.1 microM isoproterenol. Total or partial inhibition by inorganic (2 mM Mn2+, 3 mM Co2+, 1 mM Cd2+) and organic (1 microM methoxyverapamil, 5 microM diltiazem) calcium antagonists did not unmask any transient outward current. However, a consistent increase of Isi was reversibly observed with 3 mM 4-aminopyridine while using standard solutions. A second series of experiments carried out with K(+)- and Na(+)-free solutions did not demonstrate any significant change from data observed with standard solutions except a reduction of outward currents at steps above +30 mV and alteration of inactivation kinetics. In this experimental setting, 4-aminopyridine also increased Isi but to a lesser degree. We conclude that Isi, as compared to the outward currents, is dominant in the diseased human ventricular cells we have studied. |
| Databáze: | OpenAIRE |
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