Stretch-induced increases in intracellular calcium of isolated vascular smooth muscle cells.
Vascular smooth muscle responds to stretch with an increase in active force development. To investigate the role of Ca2+ in this response, we used the fluorescent dye fura-2 to quantitate changes in cytosolic Ca2+ in single, vascular smooth muscle cells during rapid stretch. Cells were enzymatically dispersed from pig coronary arteries, loaded with fura-2/AM, and studied using a digital-imaging microscope. Stretch of individual cells was accomplished by attachment with suction to two patch-type micropipettes to apply force to the ends of the cell. Stretch induced the release of Ca2+ from intracellular stores as well Ca2+ influx across the plasma membrane. In physiological saline solution containing 1.5 mM Ca2+, intracellular calcium increased with cell stretch in a sigmoidal fashion. This relationship was shifted upward in 10 mM Ca2+ bath solution and abolished after several minutes in Ca(2+)-free solution. The dihydropyridine Ca2+ channel blocker nifedipine, in doses sufficient to completely block inward Ca2+ current, produced only a partial block of the sustained stretch-induced intracellular Ca2+ response. It is concluded that in isolated pig coronary arterial smooth muscle cells, stretch-induced Ca2+ influx occurs in part via a nifedipine-resistant pathway, which may be a stretch-activated cation channel.
Davis
M J
MJ
Department of Medical Physiology and Microcirculation, College of Medicine, Texas A&M University, College Station 77843.
Meininger
G A
GA
Zawieja
D C
DC
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002469:Cell Separation; D005110:Extracellular Space / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D010812:Physical Stimulation; D013552:Swine; D014661:Vasoconstriction / Q000502:physiology*
D015220:Calcium Channels; D009543:Nifedipine; D002118:Calcium