Fig. 7
Effect of tin protoporphyrin IX (SnPP) and NG-methyl-l-arginine (l-NMA) on hemininduced relaxation in the preconstricted placental arteries. Human placental arteries were preconstricted with 100 nM U46619 (a thromboxane A2 mimetic) until steady state tension was achieved. The change of tension was examined after administration of each tested drug for 30 min. (A) Addition of 5 µM hemin to U46619-preconstricted arteries after 30-min incubation in the presence of 20 µM SnPP did not significantly reduce tension. (B) Addition of 5 µM hemin in the presence of 1 mM l-NMA significantly reduced tension. The changes of tension represent the mean ± S.E.M. of five separate experiments. *p < 0.01 vs U46619. (C) Percentage reduction in tension U46619-preconstricted arteries induced by hemin alone, hemin plus l-NMA or hemin plus SnPP. *p < 0.01 vs hemin.