Jpn. J. Pharmacol. 81 (3), 298 - 304 (1999)

Comparison of the Effects of Endothelin-1, -2 and -3 (1 - 31)
on Changes in [Ca²⁺]_i in Human Coronary Artery
Smooth Muscle Cells

Masanori Yoshizumi¹, Daisuke Inui¹, Kazuyoshi Kirima¹, Koichiro Tsuchiya¹, Hitoshi Houchi²,
Mami Azuma², Hiroaki Yasuoka¹, Hiroshi Kido³ and Toshiaki Tamaki^1,*


¹Department of Pharmacology and ²Department of Pharmacy, The University of Tokushima School of Medicine,
³Division of Enzyme Chemistry, The Institute for Enzyme Research, The University of Tokushima,
Tokushima 770 - 8503, Japan
(*) To whom correspondence should be addressed.

Abstract: We have previously found that human chymase selectively cleaves big endothelins (ETs) at the Tyr³¹-Gly³² bond to produce 31-amino-acid endothelins, ETs (1 - 31). In the present study, we investigated the effects of ETs (1 - 31) on changes in intracellular free Ca²⁺ ([Ca²⁺]_{i) in cultured human coronary artery smooth muscle cells (HCASMCs) using confocal laser microscopy. ETs (1 - 31) increased} [Ca²⁺]_{i in a concentration-dependent manner. Phosphoramidon did not inhibit the increases in} [Ca²⁺]_{i caused by ETs (1 - 31). The} [Ca²⁺]_{i increases induced by ETs (1 - 31) were compared to those of ETs (1 - 21) and big ETs. ET-1 (1 - 21) was about 10-times more potent than big ET-1 or ET-1 (1 - 31), whereas big ET-2 was 10-times less potent than ET-2 (1 - 21) or ET-2 (1 - 31). ETs (1 - 31) may induce} [Ca²⁺]_i increase through ET_A-type or ET_{A-type-like receptors. The} 10^-12 M ET (1 - 31)-induced increases in [Ca²⁺]_{i were not affected by removal of extracellular} Ca²⁺, but were inhibited by thapsigargin. These results suggested that ET-1, -2 and -3 (1 - 31) showed similar potencies in increasing [Ca²⁺]_{i and mechanisms of ET (1 - 31)-induced increases in} [Ca²⁺]_i may be similar among the three ETs (1 - 31).

Keywords: Endothelins (1 - 31), Endothelins (1 - 21), Human chymase, Confocal laser microscopy,
Intracellular free Ca²⁺