Single-channel properties of L-type calcium channels from failing human ventricle

Objective: The aim of our study was to analyse the single-channel properties of L-type calcium channels from failing human heart and to compare them to the respective animal data. Furthermore, we intended to evaluate the feasibility of future single-channel studies on the role of calcium channels in the pathophysiology of heart failure, Methods: Single L-type calcium channels were recorded in ventricular myocytes from explanted failing human heart, using the cell-attached configuration of the patch-clamp technique. Results: One or more successful registrations of calcium channels could be obtained in 11 of 19 cell isolations. Determination of single-channel conductance yielded a mean value of 16.6 +/- 1.2 pS (70 mM Ba2+ as the charge carrier) under control conditions and 23.7 +/- 2.8 pS in presence of the calcium-channel agonist FPL 64176. The rapid gating process could be described by a C <-> C <-> O gating scheme. Slow gating analysis revealed a highly significant clustering of active and non-active sweeps. Conclusion: Single-channel measurements of L-type calcium channels in human failing ventricle are feasible and reproducible despite the varying patient characteristics. Their channel properties are qualitatively comparable to those found in other mammals. Whether there are quantitative differences due to the underlying heart failure can be elucidated in further studies. (C) 1998 Elsevier Science B.V.