CONTRACTION AND INTRACELLULAR CALCIUM-ION ELEVATION OF CULTURED HUMANAORTIC SMOOTH-MUSCLE CELLS BY ENDOTHELIN-1, VASOACTIVE INTESTINAL CONTRACTOR (VIC) AND THE DERIVATIVES

Effects of endothelin (ET) family peptides and their derivatives on ce llular contraction and calcium-ion level were examined by using cultur ed human vascular smooth muscle cells (VSM). Contraction of cultured h uman VSM, isolated from human fetal aortic segments, was induced withi n 1 min after the treatment with ET-1 (100 nM) as seen in the changes of cytosolic calcium-ion localization. In parallel with the cell contr action, cytosolic calcium-ion level in the human VSM increased very ra pidly and then dropped with some oscillation as determined by Anchorag e Cell Analyzing System. It was noted that transient calcium-ion mobil ization rather than sustained calcium-ion influx was significant in th e contraction of cultured human VSM. Vasoactive intestinal contractor (VIC), three amino acids different from ET-1, had less activity in inc rease of intracellular calcium-ion level and in percent of response ce lls than ET-1, ET-2, and VIC-S4L6 (one amino acid different from ET-1) . EC50 of ET-1, VIC-S4L6, ET-2, and VIC were 0.5 nM, 0.6 nM, 2.0 nM, a nd 20 nM, respectively. VIC-like peptide (VIC-LP), 16 amino acids frag ment of VIC precursor protein, had no effect with a single administrat ion of up to 10 mu M. However, the increase in calcium-ion level by VI C was suppressed with a prior treatment of cells with high concentrati on (10 mu M) of VIC-LP. The establishment of cultured human VSM for th e simultaneous examination of the contraction and calcium-ion level wi ll provide a new system to study signal transduction of vasocontractor peptides.