Regulation of Ca2+ transport by platelet-derived growth factor-BB in rat vascular smooth muscle cells.
The present study investigates the effects of platelet-derived growth factor (PDGF) isoform BB (PDGF-BB) on cytosolic Ca2+ concentration ([Ca2+]i), Ca2+ transport, and Ca2+ pools in rat vascular smooth muscle (VSM) cells. VSM cells from thoracic aorta of Milan normotensive rats were enzymatically dispersed, cultured in 10% serum medium, and made quiescent by 72 hours in 0.3% serum medium. [Ca2+]i, Ca2+ influx, Ca2+ efflux, and exchangeable cell Ca2+ pool were evaluated by ratiometric fluorescent and radioisotope techniques. Ca2+ transport showed time-dependent changes during stimulation with PDGF-BB. The initial early responses to this peptide were transient rise in [Ca2+]i, a 30% decrease in Ca2+ influx, and a 3.6-fold increase in the rate constant for active Ca2+ efflux. Stimulation of Ca2+ efflux and inhibition of Ca2+ influx were associated with a substantial 30% reduction in the cell Ca2+ pool. This initial stimulation of Ca2+ efflux is concomitant with Ca2+ mobilization into the cytosol and is due to activation of Na(+)-independent Ca2+ efflux via the Ca2+ pump. After a 10-minute stimulation, Ca2+ influx returned to the basal value, whereas Ca2+ efflux remained 2.2-fold above control values, leading to a decline in [Ca2+]i below basal levels and a further decrease in the cell Ca2+ pool. Nearly half of this late Ca2+ efflux appears to be driven by Na(+)-Ca2+ exchange, as evidenced by its external Na+ dependence. After a 120-minute stimulation with PDGF-BB, nifedipine-sensitive Ca2+ influx is increased 37% above basal levels, and Ca2+ efflux remains elevated. During prolonged stimulation by PDGF-BB, both Ca2+ influx and efflux are stimulated, resulting in a new intracellular Ca2+ homeostasis marked by the recovery of the cell Ca2+ pool but a lowered [Ca2+]i. These final events coincide with the initiation of cell proliferation in VSM cells by PDGF-BB.
Cirillo
M
M
Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115.
Quinn
S J
SJ
Romero
J R
JR
Canessa
M L
ML
D000818:Animals; D000077214:Becaplermin; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology*; D013997:Time Factors
D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D011994:Recombinant Proteins; D000077214:Becaplermin; D002118:Calcium