Sodium and Calcium Inward Currents in Freshly Dissociated Smooth Myocytes of Rat Uterus

Journal of General Physiology - Tập 110 Số 5 - Trang 565-577 - 1997
Masami Yoshino1, S.Y. Wang1, C. Y. Kao1
1From the Department of Pharmacology, State University of New York Health Science Center, Brooklyn, New York 11203

Tóm tắt

Freshly dissociated myocytes from nonpregnant, pregnant, and postpartum rat uteri have been studied with the tight-seal patch-clamp method. The inward current contains both INa and ICa that are vastly different from those in tissue-cultured material. INa is abolished by Na+-free medium and by 1 μM tetrodotoxin. It first appears at ∼−40 mV, reaches maximum at 0 mV, and reverses at 84 mV. It activates with a voltage-dependent τ of 0.2 ms at 20 mV, and inactivates as a single exponential with a τ of 0.4 ms. Na+ conductance is half activated at −21.5 mV, and half inactivated at −59 mV. INa reactivates with a τ of 20 ms. ICa is abolished by Ca2+-free medium, Co2+ (5 mM), or nisoldipine (2 μM), and enhanced in 30 mM Ca2+, Ba2+, or BAY-K 8644. It first appears at ∼−30 mV and reaches maximum at +10 mV. It activates with a voltage-dependent τ of 1.5 ms at 20 mV, and inactivates in two exponential phases, with τ's of 33 and 133 ms. Ca2+ conductance is half activated at −7.4 mV, and half inactivated at −34 mV. ICa reactivates with τ's of 27 and 374 ms. INa and ICa are seen in myocytes from nonpregnant estrus uteri and throughout pregnancy, exhibiting complex changes. The ratio of densities of peak INa/ICa changes from 0.5 in the nonpregnant state to 1.6 at term. The enhanced role of INa, with faster kinetics, allows more frequent repetitive spike discharges to facilitate simultaneous excitation of the parturient uterus. In postpartum, both currents decrease markedly, with INa vanishing from most myocytes. Estrogen-enhanced genomic influences may account for the emergence of INa, and increased densities of INa and ICa as pregnancy progresses. Other influences may regulate varied channel expression at different stages of pregnancy.

Từ khóa


Tài liệu tham khảo

Amedee, 1987, The calcium channel current of pregnant rat single myometrial cells in short-term primary culture, J Physiol (Camb), 392, 253, 10.1113/jphysiol.1987.sp016779

Amedee, 1986, The presence of Na+channels in myometrial smooth muscle cells is revealed by specific neurotoxins, Biochem Biophys Res Commun, 137, 675, 10.1016/0006-291X(86)91131-9

Anderson, 1971, Studies in calcium and sodium in uterine smooth muscle excitation under current-clamp and voltage-clamp conditions, J Gen Physiol, 58, 322, 10.1085/jgp.58.3.322

Bolton, 1985, Patch and whole-cell voltage-clamp of single mammalian visceral and vascular smooth muscle cells, Experientia (Basel), 41, 887, 10.1007/BF01970006

Frankenhauser, 1957, The action of calcium on the electrical properties of squid axon, J Physiol (Camb), 137, 218, 10.1113/jphysiol.1957.sp005808

Hamill, 1981, Improved patch-clamp technique for high-resolution current recording from cells and cell-free membrane patches, Eur J Physiol, 391, 85, 10.1007/BF00656997

Inoue, 1991, Gestational change in Na+ and Ca2+channel current densities in rat myometrial smooth muscle cells, Am J Physiol, 29, C658, 10.1152/ajpcell.1991.260.3.C658

Inoue, 1990, Some electrical properties of human pregnant myometrium, Am J Obstet Gynecol, 162, 1090, 10.1016/0002-9378(90)91322-4

Isenberg, 1982, Calcium tolerant ventricular myocytes prepared by preincubation in a “KB” medium, Pflügers Archiv, 395, 6, 10.1007/BF00584963

Kao, 1978, A calcium current in the rat myometrium, Jpn J Smooth Muscle Res (Suppl), 14, 9

Kao, 1975, Ionic currents in the uterine smooth muscle, J Physiol (Camb), 246, 1, 10.1113/jphysiol.1975.sp010878

Kao, 1989, The outward current of the isolated rat myometrium, J Physiol (Camb), 418, 20P

Klöckner, 1985, Calcium currents of cesium loaded isolated smooth muscle cells (urinary bladder of the guinea pig), Pflügers Archiv, 405, 340, 10.1007/BF00595686

Mironneau, 1974, Voltage clamp analysis of the ionic currents in uterine smooth muscle using the double sucrose gap method, Pflügers Archiv, 352, 107, 10.1007/BF00590485

Miyoshi, 1991, Electrophysiological properties of membrane currents in single myometrial cells isolated from pregnant rats, Eur J Physiol, 419, 386, 10.1007/BF00371121

Mollard, 1986, Electrophysiological characterization of single pregnant myometrial cells in short-term primary culture, Am J Physiol, 250, C47, 10.1152/ajpcell.1986.250.1.C47

Nakai, 1983, Changing proportions of Na+ and Ca2+components of the early inward current in rat myometrium during pregnancy, Fed Proc, 42, 313

Ohya, 1989, Fast Na+ and slow Ca2+channels in single uterine muscle cells from pregnant rats, Am J Physiol, 257, C408, 10.1152/ajpcell.1989.257.2.C408

Piedras-Renteria, 1991, Potassium currents in freshly dispersed myometrial cells, Am J Physiol, 251, C278, 10.1152/ajpcell.1991.261.2.C278

Rendt, 1992, Progesterone increases Ca2+currents in myometrial cells from immature and nonpregnant adult rats, Am J Physiol, 31, C293, 10.1152/ajpcell.1992.262.2.C293

Sui, 1997, Properties of inward calcium current in guinea pig ureteral myocytes, Am J Physiol, 273, C543, 10.1152/ajpcell.1997.272.2.C543

Sui, 1993, Ca2+influx during action potentials of smooth myocytes of guinea pig urinary bladder, Biophys J, 64, A364

Suput, 1989, Ionic currents in freshly dispersed rat myometrial cells, FASEB J, 3, A254

Toro, 1990, Hormonal regulation of potassium currents in single myometrial cells, Proc Natl Acad Sci USA, 87, 2892, 10.1073/pnas.87.8.2892

Wang, 1993, Ionic currents in the uterine myocyte during pregnancy, Biophys J, 64, A366

Wang, 1996, Pregnancy and K+currents of freshly dissociated rat uterine myocytes, Biophys J, 70, A396

Yamamoto, 1989, Inward current in single cells of the guinea pig taenia coli, J Gen Physiol, 93, 521, 10.1085/jgp.93.3.521

Yang, 1994, Regulation by ovarian hormones of the large-conductance Ca2+-activated K+channels of freshly dissociated rabbit uterine myocyte, Biophys J, 66, A436

Yoshino, 1989, Ionic currents in smooth myocytes of the pregnant rat uterus, J Gen Physiol, 94, 38

Yoshino, 1990, Inward current in freshly dispersed rat myometrial cells, Biophys J, 57, 164A

Young, 1991, Characterization of sodium channels in cultured human uterine smooth muscle cells, Am J Obstet Gynecol, 164, 175, 10.1016/0002-9378(91)90650-G

Young, 1993, T-type and L-type calcium currents in freshly dispersed human uterine smooth muscle cells, Am J Obstet Gynecol, 169, 785, 10.1016/0002-9378(93)90006-5

Thông tin
Thông tin xuất bản

Journal of General Physiology

Tập 110 Số 5

565-577

Thông tin tác giả