To investigate the action mechanisms of a new erythrocyte-derived depressing factor(EDDF), the focus is placed on the effect of EDDF on both cytosolic and nuclear free calcium (Ca2+) transportation in vascular smooth muscle cell (VSMC), as well as the apoptosis and cell cycle of VSMC of rats. EDDF has been extracted from human erythrocytes. The changes of Ca2+ levels in cytoplasm ([Ca2+],) and nucleus ([Ca2+]n) have been observed using a laser scanning confocal microscope together with fluo-3/AM as a calcium indicator. Flow cytometric technique was used to study the effect of EDDF on cell cycle and apoptosis of VSMC. [Ca2+]j and [Ca2+]n were significantly decreased through several different pathways: ( i) it reduced the Ca2+ influx by blocking L-type voltage-dependent calcium channel (L-VDC) and R-type voltage-dependent calcium channel (R-VDC); (ii) it inhibited the Ca2+ release from inositol 1, 4, 5-trisphosphate (IP3) sensitive calcium store; and (iii) activated Ca2+-ATPase of sarcoplasmic reticulum ( To investigate the action mechanisms of a new erythrocyte-derived depressing factor (EDDF), the focus is placed on the effect of EDDF on both cytosolic and nuclear free calcium (Ca2 +) transportation in vascular smooth muscle cell (VSMC), as well as the The changes of Ca2 + levels in cytoplasm ([Ca2 +],) and nucleus ([Ca2 +] n) have been observed using a laser scanning confocal microscope together with fluo -3 / AM as a calcium indicator. Flow cytometric technique was used to study the effect of EDDF on cell cycle and apoptosis of VSMC. [Ca2 +] j and [Ca2 +] n were significantly decreased through several different pathways: (i) it reduced the Ca 2+ influx by blocking L-type voltage-dependent calcium channel (L-VDC) and R-type voltage-dependent calcium channel (R-VDC); (ii) it inhibited the Ca 2+ release from inositol 1, 4, 5-trisphosphate (IP3) sensitive calcium store; and (iii) activated Ca2 + -ATPase of sarcop lasmic reticulum (