Fig. 2.

Binding and cytosolic Ca²⁺. (A) Specific ¹²⁵I-ET-1 binding to NCI-H838 cells for 30 min was inhibited by increasing doses of unlabeled ET-1(○), BQ123 (•), BQ788 (■), ZD4054 (□) and ET-3 (A). The mean value ± S.D. of 3 determinations each repeated in duplicate is indicated. (B) The ability of ET-1 to alter cytosolic Ca²⁺ was investigated in Fura-2AM loaded NCI-H1975 cells. (I) ET-1, 10 nM, increased transiently the Ca²⁺ from 150 to 180 nM. The increased caused by ET-1 was antagonized by 1000 nM BQ123 (II) but not 1000 nM BQ788 (III). The block caused by BQ123 was reversed by 1000 nM but not 10 nM ET-1 (IV). This experiment is representative of 3 others.

Sequence homologies of ET-1 and ET-3 are underlined and shown below.

ET-1 CSCSSLMDKECVYFCHLDIIW

ET-3 CTCFTYKDKECVYYCHLDIIW