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Figure 4 Effects of receptor subtype antagonist or agonist on ET-1-mediated inhibition of apoptosis. Cardiac myocytes were cultured in serum-free media in the presence or absence of Iso (10^–5 mol/liter), ET-1 (10^–7 mol/liter), an ET_A receptor antagonist (FR139317), an ET_B receptor antagonist (BQ788) or an ET_B receptor agonist (IRL1620) as indicated for 48 h. The % TUNEL-positive nuclei values were calculated by counting an average of 400 to 500 nuclei in each slide. Values are mean ± SE of four independent experiments.