INCREASE IN INTRACELLULAR CALCIUM-ION IN SMOOTH-MUSCLE CELLS INDUCED BY LOW-DENSITY-LIPOPROTEIN

It was investigated whether low-density lipoprotein (LDL) had effects on intracellular Ca2+ concentration in the smooth muscle cell (SMC). L DL promoted SMC proliferation and increased intracellular Ca2+ by a tw o-phase pattern, an initial peak and a following plateau. Each phase w as suppressed by treatment with ryanodine or extracellular Ca2+-free b uffer. This increase in intracellular Ca2+ was also suppressed by anti -LDL receptor antibody. Moreover, inositol trisphosphate (IP3) was ele vated with short-term LDL treatment. Since SMC proliferation is the mo st important event in atherosclerosis and LDL is one of the main risk factors, it was concluded that LDL might trigger SMC proliferation by increasing IP3 and intracellular Ca2+ through LDL receptor.