Fig. 7. Effect of 2-APB, GF-109203X and Y-27632 on agonist-induced contraction in reconstituted rat aortic VSMC fibers. (A) High levels of K⁺ induced a contraction in the Ca²⁺-free [EGTA-containing (2 mM)] solution similar to that of the control solution containing 2 mM Ca²⁺. Y-27632 (10 µM) was added at the peak of contraction in response to the addition of high-K⁺ solution to the Ca²⁺-free solution. (B) The first contraction induced by 1 µM ATII was used as the control for the reconstituted VSMC fibers. After a 45-minute wash, the second addition of ATII resulted in a contraction to a level similar to the one after the first addition of ATII. Addition of 2-APB (30 µM) caused a faster relaxation in the presence of ATII than that by simple removal of ATII. (C) ET-1-induced contraction in the reconstituted VSMC fibers was partially inhibited by 2-APB (30 µM) alone and subsequently completely inhibited by the mixture of 2-APB and Y-27632 (10 µM). (D) ET-1-induced contraction was not affected by addition of GF-109203X (3 µM). The figures are representative of 3-5 similar experiments.