Intravenous endothelin-1 triggers pulmonary hypertension syndrome (ascites) in broilers

Two experiments were conducted to evaluate the effect of endothelin-1(ET-1) on pulmonary arterial pressure (PAP) and pulmonary hypertension syndrome (PHS, ascites) morbidity in broilers. Two hundred and seventy of one-day-old Arbor Acre commercial broiler chickens were randomly allocated into two experiments. In Experiment 1, 40 broilers (28 days of age) were intravenously with five different dose groups of ET-1, and the PAP was measured from time 0 to 30 min. The results indicated that the PAP increased from time 0.5 to 5 min after the broilers were injected with ET-1 at concentrations of 24 ng/kg (Group T1), 120 ng/kg (Group T2), and 240 ng/kg (Group T3). When the broilers were injected with ET-1 at a concentration of 360 ng/kg (Group T4), the PAP decreased immediately from time 0 to 0.5 min but increased from time 0.5 to 10 min. The change from baseline (at time 0, before the injection) of PAP values from the four treatment groups were statistically compared with that from the control group (Group C). The statistical analysis has demonstrated that there is no significant difference of the changes from the baseline between Group T1 or Group T2 and control group (Group C). However, there are significant differences in the changes between Group T3 or Group T4 and control group (Group C). In Experiment 2, 230 broilers were divided into four groups: a control group (Group C, n = 50) and three treatment groups (Groups A, B, and D). The chickens in the two treatment groups (Groups A and B, n = 60 each) were intravenously injected with ET-1 at 240 ng/kg and 360 ng/kg, respectively. Those in Group D (n = 60) were exposed to cool temperatures (10°C to 14°C). The PHS morbidity, right/total ventricular weight (RV/TV) ratio, PCV, plasma nitric oxide (NO), and PAP were recorded and statistically compared. The results showed that PHS mortality did not occur in Group C, and trends toward increases in PHS mortality in Groups A, B and D were not significant. The RV/TV ratio and PAP were higher in groups A, B and D than in group C. The values for PCV and plasma nitric oxide (NO) followed the same tendencies as the RV/TV ratio. The results suggest that ET-1 at higher doses (240 ng/kg to 360 ng/kg) can initiate pulmonary hypertension and right ventricular hypertrophy, leading to PHS in broilers.