The Effects Of BQ123 On Pulmonary Vascular Remodeling Of Low-temperature-induced Pulmonary Hypertension In Broiler Chickens

Endothelin (ET), a powerful vasoconstrictor and mitogen for smooth muscle, play a key role in human pulmonary hypertension (PH) by pulmonary vasoconstriction and pulmonary vascular remodeling (PVR). The effect of ET on PVR and PH is uncertain in ascites syndrome(AS). BQ123, a selective ETA-receptor antagonist, was used to treat broiler chickens in order to investigate the effects of ET on the PH and PVR in AS induced by low ambient temperature. Two hundred 16-day-old of age commercial broiler chickens were randomly divided into 4 groups as follows: 50 birds were exposed to normal temperature (20℃) and peritoneally injected with normal saline as control group (CG); 50 birds were exposed to low temperature (7-9℃) and peritoneally injected normal saline as low temperature group (LG); 50 birds were exposed to low temperature and peritoneally injected with low dose BQ123 as low temperature low dose BQ123 group (LLDG); 50 birds were exposed to low temperature and peritoneally injected high dose BQ123 as low temperature high dose BQ123 group (LHDG). Pulmonary arterial pressure (PAP ) was determined. The measurement of ratio of vessel wall area to vessel total area (WA/TA) and mean medial thickness in pulmonary arterioles (mMTPA) were accomplished by using the microscopic image analysis program. The percent of muscular artery (MT%), the percent of partially muscular artery (PMA%) and the percent of nonmuscular artery (NMA%) were measured and calculated under the optical microscope. The results showed as follows:1. BQ123 significantly inhibited the increase of mPAP. The mPAP of LHDG was lower than that of LG at 23 days of age (2.08±0.46kPa vs 2.89±0.9kPa, P<0.05).The mPAP of LHDG and LLDG were obviously lower than that of LG at 30 days of age (2.58±0.56kPa and 2.36±0.96kPa vs 3.7±0.44kPa, P<0.01).2. BQ123 inhibited the increase of WA/TA% of pulmonary arterioles. The WA/TA% of 30-50um pulmonary arterioles of LG(69.51 ±3.24.68.51±1.25) was obviously greater than that of LLDG (59.27 ±6.96, 58.54±5.21) and LHDG (57.89±2.95, 51.21±8.65)(P<0.01). The WA/TA% of the other ranks of pulmonary arterioles was similar.3. BQ123 inhibited the increase of mMTPA of pulmonary arterioles. The mMTPA of 30-50um pulmonary arterioles in LG was obviously greater than in LLDG and LHDG (41.35±3.04 vs33.79±3.72 and 33.34±1.61,P<0.01) at 23 days of the age. The mMTPA of LG was greater than LLDG (40.29±1.96 vs 34.61±4.95, P<0.05) and obviously greater than LHDG (40.29±156 vs 28.68±5.74, P<0.01), and LLDG was higher than LHDG (34.61±4.95 vs 28.68±5.74, P<0.05) at 30 days of the age. The mMTPA of less than 30um pulmonary arterioles was similar. It was not obviously different among groups to 50-120um pulmonary arterioles.4. BQ123 significantly inhibited the muscularization of nonmuscular pulmonary artery. The MA% and PMA% of LLDG and LHDG were obviously lower than that of LG (P<0.05, P<0.01). The NMA% of LLDG and LHDG were obviously higher than that of LG(P<0.05, P<0.01).It can be concluded that BQ123 can inhibit PVR and PH induced by low ambient temperature in broiler chickens. Therefore ET plays an important role in the development of the ascites syndrome induced by low ambient temperature.