[Direct evidences of calcium traffic through pacemaker channel].

Recently, it was shown that pacemaker f/HCN channel might be permeable not only for Na+ and K+, but also for calcium ions. Pacemaker channel HCN2 was expressed in ovarian cell culture of Chinese hamster. In the patch clamp experiments the calcium current with low amplitude 0.06±-0.87 nA and open probability 0.48% (±3.02 at -110 mV, n = 6, Ca2+ 2 mmol) was measured. HCN2-Ca2+ current significantly activated with cyclic adenosinemonophosphate by increasing of open probability and inhibited by specific If-blocker ivabradine. The calcium ion current was also shown in f-channels of neonatal rats ventriculocytes. Thus, the calcium ions conduction through HCN2 and native f-channel at physiological concentrations of extracellular fluid and physiological membrane potentials of cardiomyocytes was demonstrated.