Measurements of intracellular Ca2+ in cultured human myometrial smooth muscle cells bathed in low Na+ solutions.
In cultured human myometrial smooth muscle cells, removal of external Na+ activates repetitive increases in intracellular Ca2+ ([Ca2+]i). The Ca2+ transients persist in isotonic K+ solutions which suggests that the activity does not arise from regenerative changes in membrane potential. In nominally Ca(2+)-free solution, the activity disappears after a few cycles suggesting the involvement of internal stores. On Na+ removal, a background influx of Ca2+ may be responsible for activating the cyclical release of Ca2+ from internal stores. The absence of any effect of caffeine on resting [Ca2+]i suggests that the classical cardiac type of Ca(2+)-induced-Ca(2+)-release mechanism is not operating in these cells.
Morgan
J M
JM
Department of Physiological Sciences, Medical School, The University, Newcastle upon Tyne.
Lynn
S
S
Gillespie
J I
JI
Greenwell
J R
JR
D000328:Adult; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000032:analysis*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000737:chemistry* / Q000166:cytology*; D009215:Myometrium / Q000737:chemistry* / Q000166:cytology*; D012964:Sodium / Q000502:physiology*
D002110:Caffeine; D012964:Sodium; D002118:Calcium