AJP - Cell Physiology, Vol 260, Issue 3 C658-C663, Copyright © 1991 by American Physiological Society

ARTICLES

Gestational change in Na+ and Ca2+ channel current densities in rat myometrial smooth muscle cells

Y. Inoue and N. Sperelakis
Department of Physiology and Biophysics, University of Cincinnati College of Medicine, Ohio 45267-0576.

The change of Na+ and Ca2+ channel currents during gestation was investigated using the whole cell voltage-clamp method on single smooth muscle cells freshly isolated from the longitudinal layer of pregnant rat uterus. The current-voltage relationships for both the Na+ and Ca2+ currents did not change during gestation. The threshold voltage, the voltage at the peak inward current, and the reversal potential (extrapolated) were virtually identical. The averaged current densities of Ca2+ channel were almost unchanged between days 9 and 21; this value at day 5 was somewhat lower. In contrast, the averaged current density of fast Na+ channels increased markedly in the myometrium during gestation: from 0 at day 5 to 0.19 +/- 0.16 at day 9, to 0.56 +/- 0.13 at day 14, to 0.90 +/- 0.13 at day 18, and to 0.86 +/- 0.14 pA/pF at day 21. This almost linear increase in the averaged density of fast Na+ channels during gestation occurs because of an increase in the fraction of cells which possessed fast Na+ channels. These results suggest that the role of fast Na+ channels in myometrial activity becomes more and more important as term approaches. We suggest that the fast Na+ current may be involved in spread of excitation.

This article has been cited by other articles:

				W. X. Wu, Q. Zhang, N. Unno, J. B. Derks, and P. W. Nathanielsz Characterization of decorin mRNA in pregnant intrauterine tissues of the ewe and regulation by steroids Am J Physiol Cell Physiol, January 1, 2000; 278(1): C199 - C206. [Abstract] [Full Text] [PDF]

				C. Martin, J.-M. Hyvelin, K. E. Chapman, R. Marthan, R. H. Ashley, and J.-P. Savineau Pregnant rat myometrial cells show heterogeneous ryanodine- and caffeine-sensitive calcium stores Am J Physiol Cell Physiol, August 1, 1999; 277(2): C243 - C252. [Abstract] [Full Text] [PDF]

				H. KURIYAMA, K. KITAMURA, T. ITOH, and R. INOUE Physiological Features of Visceral Smooth Muscle Cells, With Special Reference to Receptors and Ion Channels Physiol Rev, July 1, 1998; 78(3): 811 - 920. [Abstract] [Full Text] [PDF]

				M. Gomez and K. Sward Long-term regulation of contractility and calcium current in smooth muscle Am J Physiol Cell Physiol, November 1, 1997; 273(5): C1714 - C1720. [Abstract] [Full Text] [PDF]

				K. D. Dunlap, M. L. McAnelly, and H. H. Zakon Estrogen Modifies an Electrocommunication Signal by Altering the Electrocyte Sodium Current in an Electric Fish, Sternopygus J. Neurosci., April 15, 1997; 17(8): 2869 - 2875. [Abstract] [Full Text] [PDF]