Biol Reprod Keystone Symposia Conference on Frontiers in Reproductive Biology & Regulation of Fertility.
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BOR - Papers in Press, published online ahead of print August 1, 2007.
Biol Reprod 2007, 10.1095/biolreprod.107.063016
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BIOLOGY OF REPRODUCTION 77, 855–863 (2007)
DOI: 10.1095/biolreprod.107.063016
© 2007 by the Society for the Study of Reproduction, Inc.

Functional and Molecular Characterization of Voltage-Gated Sodium Channels in Uteri from Nonpregnant Rats1

Marian Seda 3, Francisco M Pinto 3, Susan Wray 4, Cristina G Cintado 3, Pedro Noheda 5, Helmut Buschmann 6, and Luz Candenas 2 3

Instituto de Investigaciones Químicas,3 41092 Sevilla, Spain Department of Physiology,4 The University of Liverpool, Liverpool L69 3BX, United Kingdom Instituto de Química Orgánica General,5 CSIC, 28006 Madrid, Spain Laboratorios del Dr. Esteve,6 08041 Barcelona, Spain

ABSTRACT

We investigated the function and expression of voltage-gated Na+ channels (VGSC) in the uteri of nonpregnant rats using organ bath techniques, intracellular [Ca2+] fluorescence measurements, and RT-PCR. In longitudinally arranged whole-tissue uterine strips, veratridine, a VGSC activator, caused the rapid appearance of phasic contractions of irregular frequency and amplitude. After 50–60 min in the continuous presence of veratridine, rhythmic contractions of very regular frequency and slightly increasing amplitude occurred and were sustained for up to 12 h. Both the early and late components of the contractile response to veratridine were inhibited in a concentration-dependent manner by tetrodotoxin (TTX). In small strips dissected from the uterine longitudinal smooth muscle layer and loaded with Fura-2, veratridine also caused rhythmic contractions, accompanied by transient increases in [Ca2+]i, which were abolished by treatment with 0.1 µM TTX. Using end-point and real-time quantitative RT-PCR, we detected the presence of the VGSC alpha subunits Scn2a1, Scn3a, Scn5a, and Scn8a in the cDNA from longitudinal muscle. The mRNAs of the auxiliary beta subunits Scbn1b, Scbn2b, Scbn4b, and traces of Scn3b were also present. These data show for the first time that Scn2a1, Scn3a, Scn5a, and Scn8a, as well as all VGSC beta subunits are expressed in the longitudinal smooth muscle layer of the rat myometrium. In addition, our data show that TTX-sensitive VGSC are able to mediate phasic contractions maintained over long periods of time in the uteri of nonpregnant rats.

female reproductive tract, signal transduction, uterus

FOOTNOTES

1Supported by a grant from Laboratorios del Dr. Esteve (Barcelona, Spain), and fellowships from Laboratorios del Dr. Esteve (to M.S.) and the MRC (to S.W).

Correspondence: 2Correspondence: Luz Candenas, Instituto de Investigaciones Químicas, Avda Americo Vespucio 49, 41092 Sevilla, Spain. FAX: 34 95 446 0565; e-mail: luzcandenas{at}iiq.csic.es






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Copyright © 2007 by the Society for the Study of Reproduction.