passages.id: split_5_test_2135_passage
passages.type: progene_text
passages.text: Preincubation with the ET(A) receptor antagonist FR139317 ( 1 microM ) decreased significantly ( P < 0.005 ) the potency of ET - I in both atrial and ventricular trabeculae , without any significant changes in Emax ( maximum effect obtained with an agonist ) .