Role of T-type Ca<SUP>2+</SUP> Channels in the Spontaneous Phasic Contraction of Pregnant Rat Uterine Smooth Muscle
Role of T-type Ca<SUP>2+</SUP> Channels in the Spontaneous Phasic Contraction of Pregnant Rat Uterine Smooth Muscle
- Si-Eun Lee Duck-Sun Ahn Young-Ho Lee
- 대한생리학회-대한약리학회
- The Korean Journal of Physiology & Pharmacology
- 제13권 제3호
- 등재여부 : KCI등재
- 2009.01
- 241 - 249 (9 pages)
Although extracellular Ca<sup>2+</sup> entry through the voltage-dependent Ca<sup>2+</sup> channels plays an important role in the spontaneous phasic contractions of the pregnant rat myometrium, the role of the T-type Ca<sup>2+</sup> channels has yet to be fully identified. The aim of this study was to investigate the role of the T-type Ca<sup>2+</sup> channel in the spontaneous phasic contractions of the rat myometrium. Spontaneous phasic contractions and [Ca<sup>2+</sup>]<sub>i</sub> were measured simultaneously in the longitudinal strips of female Sprague-Dawley rats late in their pregnancy (on day 18∼20 of gestation: term=22 days). The expression of T-type Ca<sup>2+</sup> channel mRNAs or protein levels was measured. Cumulative addition of low concentrations (<1ՌM) of nifedipine, a L-type Ca<sup>2+</sup> channel blocker, produced a decrease in the amplitude of the spontaneous Ca<sup>2+</sup> transients and contractions with no significant change in frequency. The mRNAs and proteins encoding two subunits (Ձ1G, Ձ1H) of the T-type Ca<sup>2+</sup> channels were expressed in longitudinal muscle layer of rat myometrium. Cumulative addition of mibefradil, NNC 55-0396 or nickel induced a concentration-dependent inhibition of the amplitude and frequency of the spontaneous Ca<sup>2+</sup> transients and contractions. Mibefradil, NNC 55-0396 or nickel also attenuated the slope of rising phase of spontaneous Ca<sup>2+</sup> transients consistent with the reduction of the frequency. It is concluded that T-type Ca<sup>2+</sup> channels are expressed in the pregnant rat myometrium and may play a key role for the regulation of the frequency of spontaneous phasic contractions.