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Myometrial relaxation of mice via expression of two pore domain acid sensitive K + (TASK-2) channels

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ABSTRACT

Myometrial relaxation of mouse via expression of two-pore domain acid sensitive (TASK) channels was studied. In our previous report, we suggested that two-pore domain acid-sensing K+ channels (TASK-2) might be one of the candidates for the regulation of uterine circular smooth muscles in mice. In this study, we tried to show the mechanisms of relaxation via TASK-2 channels in marine myometrium. Isometric contraction measurements and patch clamp technique were used to verify TASK conductance in murine myometrium. Western blot and immunehistochemical study under confocal microscopy were used to investigate molecular identity of TASK channel. In this study, we showed that TEA and 4-AP insensitive non-inactivating outward K+ current (NIOK) may be responsible for the quiescence of murine pregnant longitudinal myometrium. The characteristics of NIOK coincided with two-pore domain acid-sensing K+ channels (TASK-2). NIOK in the presence of K+ channel blockers was inhibited further by TASK inhibitors such as quinidine, bupivacaine, lidocaine, and extracellular acidosis. Furthermore, oxytocin and estrogen inhibited NIOK in pregnant myometrium. When compared to non-pregnant myometrium, pregnant myometrium showed stronger inhibition of NIOK by quinidine and increased immunohistochemical expression of TASK-2. Finally, TASK-2 inhibitors induced strong myometrial contraction even in the presence of L-methionine, a known inhibitor of stretch-activated channels in the longitudinal myometrium of mouse. Activation of TASK-2 channels seems to play an essential role for relaxing uterus during pregnancy and it might be one of the alternatives for preventing preterm delivery.

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Regulation of pregnant mouse myometrial contractility by TASK-2 channel inhibitors in the presence of TEA and 4-AP.The TASK-2 inhibitors produced contractions in pregnant myometrium in the presence of TEA and 4-AP. (A) Extracellular acidosiso (pHo=6.4) produced contractions in pregnant myometrium. (B) Bupivacaine (100 nM) also produced robust contractions even in the presence of nerve blockers. (C) L-methionine (1 mM), which inhibits stretch-dependent K2P channels (TREK-1), produced contractions that spontaneously decayed to near baseline values within 10~15 min. However, lidocaine produced robust contraction in the presence of L-methionine. (D~E) Data are summarized.
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Figure 2: Regulation of pregnant mouse myometrial contractility by TASK-2 channel inhibitors in the presence of TEA and 4-AP.The TASK-2 inhibitors produced contractions in pregnant myometrium in the presence of TEA and 4-AP. (A) Extracellular acidosiso (pHo=6.4) produced contractions in pregnant myometrium. (B) Bupivacaine (100 nM) also produced robust contractions even in the presence of nerve blockers. (C) L-methionine (1 mM), which inhibits stretch-dependent K2P channels (TREK-1), produced contractions that spontaneously decayed to near baseline values within 10~15 min. However, lidocaine produced robust contraction in the presence of L-methionine. (D~E) Data are summarized.

Mentions: Because quinidine is a potent inhibitor of two-pore domain channels (TASK; IC50=22 µM for TASK-2 of expressed cell) [24], we also studied the effects of other TASK channel inhibitors such as lidocaine (1 mM), bupivacaine (100 nM), and [pH]o=6.4. All of these TASK channel inhibitors increased contractility in pregnant longitudinal myometrium (Fig. 2) [21]. To rule out the involvement of other K+ channels, TEA (10 mM) and 4-AP (5 mM) was also used. TASK channels in pregnant myometrium were inhibited with bupivacaine and [pH]o=6.4 in the presence of TEA (10 mM) and 4-AP (5 mM). As shown in Fig. 2A and 2D, [pH]o=6.4 and bupivacaine provoked contractions in the presence of TEA and 4-AP. [pH]o=6.4 and bupivacaine also provoked contractions in the presence of nerve blockers as well as TEA and 4-AP (Fig. 2B and 2D).


Myometrial relaxation of mice via expression of two pore domain acid sensitive K + (TASK-2) channels
Regulation of pregnant mouse myometrial contractility by TASK-2 channel inhibitors in the presence of TEA and 4-AP.The TASK-2 inhibitors produced contractions in pregnant myometrium in the presence of TEA and 4-AP. (A) Extracellular acidosiso (pHo=6.4) produced contractions in pregnant myometrium. (B) Bupivacaine (100 nM) also produced robust contractions even in the presence of nerve blockers. (C) L-methionine (1 mM), which inhibits stretch-dependent K2P channels (TREK-1), produced contractions that spontaneously decayed to near baseline values within 10~15 min. However, lidocaine produced robust contraction in the presence of L-methionine. (D~E) Data are summarized.
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Related In: Results  -  Collection

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Figure 2: Regulation of pregnant mouse myometrial contractility by TASK-2 channel inhibitors in the presence of TEA and 4-AP.The TASK-2 inhibitors produced contractions in pregnant myometrium in the presence of TEA and 4-AP. (A) Extracellular acidosiso (pHo=6.4) produced contractions in pregnant myometrium. (B) Bupivacaine (100 nM) also produced robust contractions even in the presence of nerve blockers. (C) L-methionine (1 mM), which inhibits stretch-dependent K2P channels (TREK-1), produced contractions that spontaneously decayed to near baseline values within 10~15 min. However, lidocaine produced robust contraction in the presence of L-methionine. (D~E) Data are summarized.
Mentions: Because quinidine is a potent inhibitor of two-pore domain channels (TASK; IC50=22 µM for TASK-2 of expressed cell) [24], we also studied the effects of other TASK channel inhibitors such as lidocaine (1 mM), bupivacaine (100 nM), and [pH]o=6.4. All of these TASK channel inhibitors increased contractility in pregnant longitudinal myometrium (Fig. 2) [21]. To rule out the involvement of other K+ channels, TEA (10 mM) and 4-AP (5 mM) was also used. TASK channels in pregnant myometrium were inhibited with bupivacaine and [pH]o=6.4 in the presence of TEA (10 mM) and 4-AP (5 mM). As shown in Fig. 2A and 2D, [pH]o=6.4 and bupivacaine provoked contractions in the presence of TEA and 4-AP. [pH]o=6.4 and bupivacaine also provoked contractions in the presence of nerve blockers as well as TEA and 4-AP (Fig. 2B and 2D).

View Article: PubMed Central - PubMed

ABSTRACT

Myometrial relaxation of mouse via expression of two-pore domain acid sensitive (TASK) channels was studied. In our previous report, we suggested that two-pore domain acid-sensing K+ channels (TASK-2) might be one of the candidates for the regulation of uterine circular smooth muscles in mice. In this study, we tried to show the mechanisms of relaxation via TASK-2 channels in marine myometrium. Isometric contraction measurements and patch clamp technique were used to verify TASK conductance in murine myometrium. Western blot and immunehistochemical study under confocal microscopy were used to investigate molecular identity of TASK channel. In this study, we showed that TEA and 4-AP insensitive non-inactivating outward K+ current (NIOK) may be responsible for the quiescence of murine pregnant longitudinal myometrium. The characteristics of NIOK coincided with two-pore domain acid-sensing K+ channels (TASK-2). NIOK in the presence of K+ channel blockers was inhibited further by TASK inhibitors such as quinidine, bupivacaine, lidocaine, and extracellular acidosis. Furthermore, oxytocin and estrogen inhibited NIOK in pregnant myometrium. When compared to non-pregnant myometrium, pregnant myometrium showed stronger inhibition of NIOK by quinidine and increased immunohistochemical expression of TASK-2. Finally, TASK-2 inhibitors induced strong myometrial contraction even in the presence of L-methionine, a known inhibitor of stretch-activated channels in the longitudinal myometrium of mouse. Activation of TASK-2 channels seems to play an essential role for relaxing uterus during pregnancy and it might be one of the alternatives for preventing preterm delivery.

No MeSH data available.


Related in: MedlinePlus