Ca 2+-dependence of endothelin-1 induced contraction of rat tail artery

Abstract

1. 1. In rat tail artery, endothelin-1(ET-1) caused an increase in the cytosolic free Ca 2+ level ([Ca 2+] i) followed by a relatively sustained but not steady-state contraction in Ca 2+ containing solution. 2. 2. In the early phase of the contraction, the rate of increase in [Ca 2+] i was much faster than that in muscle tension. However, after the increases in [Ca 2+] i and muscle tension reached at their peaks, there was a good correlation between the changes of the two parameters. 3. 3. ET-1 could not induce an apparent contractile response in Ca 2+-free medium, notwithstanding it evoked a [Ca 2+] i transient in this medium. 4. 4. The results indicate that ET-1 induce a contraction of rat tail artery which is almost fully dependent on the [Ca 2+] i changes, and may inhibit the Ca 2+-sensitivity of the contractile filaments in the early phase of the contraction.