Primary Study Of The Relationship Between The Hypoxia Inducible Factor-1α And Ascites Syndrome In Broilers

Pulmonary hypertension syndrome (PHS) in broiler chickens poses a serious problem to the international poultry industry worldwide, and is an important cause of mortality that has been reported from many parts of the world. For broilers kept at altitudes of proximately3000m, the onset of pulmonary hypertension, cardiac hypertrophy, heart failure, and oedema leading to PHS has been described. More recently similar symptoms and mortality were reported in broilers reared at lower altitudes of1000to2000m and at altitudes down to sea level. It represents a cost to the industry of about one billion＄annually. It has been suggested that the fast-growing modem broiler is particularly susceptible to PHS, because rapid growth causes an increased demand for oxygen, which forces the heart to maintain an elevated cardiac output. The resulting increase in blood pressure within the pulmonary circulation can cause hypertrophy of the right ventricle and eventually congestive heart failure. This pathogenesis for PHS includes increased oxygen requirements by body tissues and low oxygen tensions in arterial blood. Further pathologic mechanism is not clear. The present study was conducted to further evaluate the pathogenesis of the acute and chronic form of PHS, the role of hypoxia inducible factor-1in broilers with PHS, and to obtain new methods preventing PHS.Test I The change of physiological and biochemical indexes in ascites broilers induced by low ambient temperature and added triiodothyronine (T3) to the diet. One hundred and sixty Avian commercial broilers were randomly distributed to two groups. The group reared under normal ambient temperature served as NT group. The other group was exposed to low ambient temperature and added three triiodothyronine (T3) to the diet (LT+T3group) in order to induce pulmonary hypertension syndrome (PHS) from day14on. The ratio of right ventricular weight to total ventricular weight (RV/TV), red blood cell count (RBC), packed cell volume (PCV), hemoglobin (Hb), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), creatine kinase(CK), alkaline phosphatase (AKP) and uric acid (UA) were measured at22,29,36and43-day-old of age, respectively. The results showed that the lower ambient temperature and dietary T3adding significantly increased PHS incidence (P<0.01), the RV/TV was significantly increased (P<0.05) after day29. RBC、PCV、Hb、 AST and AKP indexes were significantly changed at day29, day29, day36, day22, day22(P<0.05), respectively. The results indicate that RBC、PCV、 Hb、and AKP indexes are useful for diagnosing PHS in broiler.Test Ⅱ Expression of HIF-la in the lung and its association with antioxidant capacity in broilers with pulmonary hypertension. The present study was conducted to examine the expression of HIF-1α in the respiratory capillary of pulmonary hypertension broilers and the association between HIF-1α and antioxidant capacity. One hundred and sixty14day-old Avian commercial broilers were randomly equally distributed to two groups (NT group, and LT+T3group). PHS incidence was recorded. The ratio of right ventricle to total ventricle (RV/TV), SOD, MDA and T-AOC were measured on22,29,36,43days of age, respectively, and expression of HIF-la in the respiratory capillary labeled by immunohistochemistry and quantified by measuring optical density (OD) using computer-image analytic software. The results indicated that the lower ambient temperature and dietary T3adding significantly increased PHS incidence (P<0.01), the OD value was significantly increased (P<0.05) after day29, MDA was significantly increased (P<0.01) after day29, while SOD and T-AOC were significantly decreased in serum (P<0.05). It demonstrated that HIF-la has been involved in the formation of PHS and had negative relationship with antioxidant capacity.Test III Role of hypoxia inducible factor-la and VEGF in the development of ascites syndrome in broilers. Ten ascites broilers and ten healthy broilers were selected from LT+T3group and NT group to observe the ratio of right ventricle to total ventricle (RV/TV) and pathological changes by HE and Elastin stained methods, to determine pulmonary vascular remodeling by the microscopic image analysis program. The expression of the HIF-la and VEGF labeled by immunohistochemical techniques and quantified by measuring optical density (OD) using computer-image analytic software. Edema was seen in the pulmonary of the ascites group, but it was not seen in the healthy group. The mMTPA and TWPV%below of60μm pulmonary arterioles in the ascites group was obviously higher than that in the healthy group (P<0.01). Optical density of HIF-1α and VEGF of the ascites group was more than that of healthy group in the atrium and respiratory capillary of pulmonary arterioles. It was concluded that HIF-1α plays an important role in the development of pulmonary vascular remodeling in aseites broilers.