Role of T-type Ca2+ Channels in the Spontaneous Phasic Contraction of Pregnant Rat Uterine Smooth Muscle.
10.4196/kjpp.2009.13.3.241
- Author:
Si Eun LEE
1
;
Duck Sun AHN
;
Young Ho LEE
Author Information
1. Department of Physiology, BK 21 Project for Medical Sciences, College of Medicine, Yonsei University, Seoul 120-752, Korea. yhlee@yumc.yonsei.ac.kr
- Publication Type:Original Article
- Keywords:
Calcium channels;
Nickel;
Mibefradil;
NNC 55-0396;
Spontaneous contractility
- MeSH:
Animals;
Benzimidazoles;
Calcium Channels;
Contracts;
Cyclopropanes;
Female;
Humans;
Mibefradil;
Mice;
Muscle, Smooth;
Muscles;
Myometrium;
Naphthalenes;
Nickel;
Nifedipine;
Pregnancy;
Proteins;
Rats;
Rats, Sprague-Dawley;
RNA, Messenger
- From:The Korean Journal of Physiology and Pharmacology
2009;13(3):241-249
- CountryRepublic of Korea
- Language:English
-
Abstract:
Although extracellular Ca2+ entry through the voltage-dependent Ca2+ channels plays an important role in the spontaneous phasic contractions of the pregnant rat myometrium, the role of the T-type Ca2+ channels has yet to be fully identified. The aim of this study was to investigate the role of the T-type Ca2+ channel in the spontaneous phasic contractions of the rat myometrium. Spontaneous phasic contractions and [Ca2+]i 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 Ca2+ channel mRNAs or protein levels was measured. Cumulative addition of low concentrations (<1 micrometer) of nifedipine, a L-type Ca2+ channel blocker, produced a decrease in the amplitude of the spontaneous Ca2+ transients and contractions with no significant change in frequency. The mRNAs and proteins encoding two subunits (alpha1G, alpha1H) of the T-type Ca2+ 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 Ca2+ transients and contractions. Mibefradil, NNC 55-0396 or nickel also attenuated the slope of rising phase of spontaneous Ca2+ transients consistent with the reduction of the frequency. It is concluded that T-type Ca2+ channels are expressed in the pregnant rat myometrium and may play a key role for the regulation of the frequency of spontaneous phasic contractions.
