EFFECTS OF SHORT-TERM AND LONG-TERM EXPOSURE TO LINOLEIC-ACID HYDROPEROXIDE ON CYTOSOLIC CALCIUM-ION LEVEL OF HUMAN AORTIC INTIMAL SMOOTH-MUSCLE CELLS IN-VITRO

When cultured intimal smooth muscle cells from human aorta were expose d for a short period of time (25 sec) to linoleic acid hydroperoxide ( 100 nmol/ml), influx of calcium ions into the cytosol of these cells w as provoked, and a temporal increase in cytosolic calcium ion level wa s observed. Two calcium channel blockers inhibited this influx. Long-t erm exposure (4 min) of these cells to the hydroperoxide also provoked the influx of calcium ions, which resulted in a longer time of the ca lcium ion increase. In the latter case, however, the calcium channel b locker inhibited the initial influx, but then the influx started and c ontinued even in the presence of the blocker. Such difference in expos ure time-dependent effects should be taken into account in considering pathological roles of lipid hydroperoxides.