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Modulation of uterine excitability by small conductance Ca 2+ ‐activated K + (SK3) channel expression during pregnancy
Author(s) -
Taylor Mark Stephen,
Brown Amber,
Cornwell Trudy,
Solodushko Viktoriya
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a1300-b
Subject(s) - apamin , endocrinology , myometrium , medicine , nifedipine , uterine contraction , pregnancy , chemistry , contraction (grammar) , conductance , uterus , biology , potassium channel , calcium , physics , genetics , condensed matter physics
Mechanisms controlling uterine excitability over the course of pregnancy are not well understood. Here, we determine whether changes in the expression of small conductance Ca 2+ ‐activated K + channels (SK3) in the myometrium over the course of gestation influence phasic uterine contraction. Longitudinal uterine strips were isolated from female mice in three groups: Non‐pregnant (NP), Mid‐Pregnant (MP; day 6‐16) and Term‐pregnant (TP; day 19‐20). Uterine SK3 expression was increased (2.3‐fold) in MP compared to NP mice and decreased (4.8‐fold) in TP mice compared to MP mice. Immunostaining revealed prominent SK3‐positive signal within longitudinal muscle layers. In functional experiments, MP uterine strips exhibited low‐grade, erratic spontaneous contractions compared to periodic contractions in NP, and particularly strong, coordinated contractions in TP strips. All contractions were abolished by the L‐type Ca 2+ channel inhibitor nifedipine (1μM). Addition of the selective SK channel blocker apamin (0.3μM) enhanced contractions to a greater degree in MP (88±28%) compared to NP (24±6%) strips (p<0.05), and had no effect on TP strips. These data suggest that an increase in myometrial SK3 channel expression during mid‐pregnancy favors uterine quiescence whereas an abrupt decrease in SK3 channel expression at term promotes strong, coordinated contractions required for parturition.