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"];), Ca' transport, and Ca' 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"Jj, Ca' influx, Ca' 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 a transient rise in [Ca2+1], a 30% decrease in Ca2+ influx, and a 3.6-fold increase in the rate constant for active Ca>2 efflux. Stimulation of Ca>2 efflux and inhibition of Ca2+ influx were associated with a substantial 30%o 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 Ca>2 pump. After a 10 -minute stimulation, Ca 2+ influx returned to the basal value, whereas Ca2+ efflux remained 2.2-fold above control values, leading to