Action potentials in primary osteoblasts and in the MG-63 osteoblast-like cell line

Abstract

Whole-cell patch-clamp analysis revealed a resting membrane potential of −60 mV in primary osteoblasts and in the MG-63 osteoblast-like cells. Depolarization-induced action potentials were characterized by duration of 60 ms, a minimal peak-to-peak distance of 180 ms, a threshold value of −20 mV and a repolarization between the spikes to −45 mV. Expressed channels were characterized by application of voltage pulses between −150 mV and 90 mV in 10 mV steps, from a holding potential of −40 mV. Voltages below −60 mV induced an inward current. Depolarizing voltages above −30 mV evoked two currents: (a) a fast activated and inactivated inward current at voltages between −30 and 30 mV, and (b) a delayed-activated outward current that was induced by voltages above −30 mV. Electrophysiological and pharmacological parameters indicated that hyperpolarization activated strongly rectifying K+ (Kir) channels, whereas depolarization activated tetrodotoxin sensitive voltage gated Na+ (Nav) channels as well as delayed, slowly activated, non-inactivating, and tetraethylammonium sensitive voltage gated K+ (Kv) channels. In addition, RT-PCR showed expression of Nav1.3, Nav1.4, Nav1.5, Nav1.6, Nav1.7, and Kir2.1, Kir2.3, and Kir2.4 as well as Kv2.1. We conclude that osteoblasts express channels that allow firing of action potentials. The final publication is available at Springer via https://doi.org/10.1007/s10863-011-9354-7.