Molecular and biophysical properties of voltage-gated Na+ channels in murine vas deferens.
The biological and molecular properties of tetrodotoxin (TTX)-sensitive voltage-gated Na(+) currents (I(Na)) in murine vas deferens myocytes were investigated using patch-clamp techniques and molecular biological analyses. In whole-cell configuration, a fast, transient inward current was evoked in the presence of Cd(2+), and was abolished by TTX (K(d) = 11.2 nM), mibefradil (K(d) = 3.3 microM), and external replacement of Na(+) with monovalent cations (TEA(+), Tris(+), and NMDG(+)). The fast transient inward current was enhanced by veratridine, an activator of voltage-gated Na(+) channels, suggesting that the fast transient inward current was a TTX-sensitive I(Na). The values for half-maximal (V(half)) inactivation and activation of I(Na) were -46.3 mV and -26.0 mV, respectively. RT-PCR analysis revealed the expression of Scn1a, 2a, and 8a transcripts. The Scn8a transcript and the alpha-subunit protein of Na(V)1.6 were detected in smooth muscle layers. Using Na(V)1.6-null mice (Na(V)1.6(-/-)) lacking the expression of the Na(+) channel gene, Scn8a, I(Na) were not detected in dispersed smooth muscle cells from the vas deferens, while TTX-sensitive I(Na) were recorded in their wild-type (Na(V)1.6(+/+)) littermates. This study demonstrates that the molecular identity of the voltage-gated Na(+) channels responsible for the TTX-sensitive I(Na) in murine vas deferens myocytes is primarily Na(V)1.6.
Zhu
Hai-Lei
HL
Department of Pharmacology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Aishima
Manami
M
Morinaga
Hidetaka
H
Wassall
Richard D
RD
Shibata
Atsushi
A
Iwasa
Kazuomi
K
Nomura
Masatoshi
M
Nagao
Masaya
M
Sueishi
Katsuo
K
Cunnane
Thomas C
TC
Teramoto
Noriyoshi
N
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002478:Cells, Cultured; D015640:Ion Channel Gating / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000502:physiology*; D014649:Vas Deferens / Q000502:physiology*
D015222:Sodium Channels; D012964:Sodium