Properties of voltage-activated [Ca2+](i) transients in single smooth muscle cells isolated from pregnant rat uterus

A. V. Shmigol, D. A. Eisner, Susan Wray

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74 Citations (Scopus)

Abstract

1. The intracellular calcium concentration ([Ca2+](i)) was measured at 35°C using the fluorescent indicator indo-1 in patch-clamped, single uterine myocytes from pregnant rats to investigate the relationship between depolarization, Ca2+ current (I(Ca)) and [Ca2+](i). 2. Membrane depolarization activated I(Ca) and produced a [Ca2+](i) transient. The rapid increase in [Ca2+](i) occurred at the same time as the inward I(Ca). Both I(Ca) and the increase in [Ca2+](i) were abolished by nifedipine (10 μM). 3. When the membrane potential was held at -80 mV the threshold depolarization for an increase in [Ca2+](i) was about -55 to -50 mV. As the magnitude of the depolarization was increased to about 0 mV there was an increase in the size of both I(Ca) and the increase in [Ca2+](i). As the magnitude of tire depolarization was further increased both I(Ca) and the [Ca2+](i) increase declined. 4. When the depolarizing pulses were applied at 3 Hz to mimic normal action potentials then the individual [Ca2+](i) transients did not fully relax and a tetanic rise of [Ca2+](i) was observed. Under these conditions, there was not a simple relationship between the magnitude of the Ca2+ response and Ca2+ entry. When pairs of depolarizing pulses were applied, the increase in [Ca2+](i) produced by the second pulse was larger (in relation to the magnitude of the L-type Ca2+ current) than that produced by the first pulse. This facilitation was abolished by both ryanodine and cyclopiazonic acid suggesting a role for release from intracellular stores. 5. We conclude that the L-type Ca2+ current is the major source of Ca2+ ions entering the cell to produce the [Ca2+](i) transient on depolarization. The magnitude of the increase in [Ca2+](i) may, however, be amplified by Ca2+-induced Ca2+ release.

Original languageEnglish
Pages (from-to)803-811
Number of pages9
JournalJournal of Physiology
Volume511
Issue number3
DOIs
Publication statusPublished - Sep 15 1998
Externally publishedYes

ASJC Scopus subject areas

  • Physiology

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