RESUMO
To investigate the effect of T(3)-induced pulmonary hypertension on endothelin (ET) production and genes expression of ET-1, ET(A) and ET(B) receptors (ET(A)R and ET(B)R) during rearing, semiquantitative RT-PCR and enzyme immunometric assay were performed in the heart ventricles and serum, respectively. The ET-1 and its receptor genes were expressed in the right and left ventricles of control and T(3)-treated broilers at 12, 28 and 49 days of age. There were significant (P<0.05) reductions of the relative amounts of ET-1 (in both ventricles) and ET(A)R (in the right ventricle) mRNAs at 28 and 49 days of age, in T(3)-treated broilers compared to controls. The relative amounts of ET(B)R mRNA in the right and left ventricles did not significantly differ between control and T(3)-treated broilers at any age. The serum level of ET was significantly (P<0.05) increased in T(3)-treated chickens at 28 and 49 days of age when compared with that of the control. It is concluded that ET-1, ET(A)R and ET(B)R genes are normally expressed in the heart ventricles of broilers. It is likely that increased serum level of ET and decreased ET-1/ET(A)R genes expression in the ventricles are involved in the heart dysfunction of broiler chickens with developmental pulmonary hypertension.