Influence of asphyxia on myocardial β-adrenergic receptor in neonatal mice

Li Changjian; Xi Shibing; Li Tao

doi:10.3969/j.issn.1674-4055.2017.07.08

Abstract：Objective To investigate the influence of asphyxia on expression of myocardial β-adrenergic receptor and interventional effect on β2-adrenoceptor agonist in neonatal mice.Methods Clean ICR mice (n=108, male or female) born for 3 d were randomly divided into normal group put into wide-mouth bottle without any treatment, asphyxia group prepared to ordinary pressure asphyxia model according to literature method, and intervention group given intraperitoneal injection of fenoterol 2 h before asphyxia (eachn=36). The mice (n=6) were randomly chosen from each group on the 3rd d, 5th d, 7th d, 14th d, 21st d and 28th d for detecting electrocardiogram (ECG) and calculating heart weight index (HW/BW). The samples of cardiac tissue were collected for detecting the expressions of β1-adrenergic receptor and β2-adrenergic receptor by using immunohistochemistry technique and Western blot.Results The results of immunohistochemistry staining ofβ1-adrenergic receptor in normal mice showed that alignment myocardial cells, distinct nucleus and intact cell membrane without inflammatory cell infiltration. The staining of cell nuclear envelope and plasma darkened as the age of mice increased (from 3 d to 28 d). The results of Western blot showed that relative expression of β1-adrenergic receptor was significantly higher in 28-d mice than that in 3-d mice (P<0.05). The staining of β2-adrenergic receptor showed that staining of cell nuclear envelope and plasma became shallow as the age of mice increased. The results of Western blot showed that relative expression of β2-adrenergic receptor was significantly lower in 28 d mice than that in 3 d mice (P<0.05). The staining of β1-adrenergic receptor and β2-adrenergic receptor became shallow, and expressions of them decreased significantly in asphyxia group compared with normal group on the 3rd d, and there were malalignment myocardial cells and a few exudate inflammatory cells observed in asphyxia group. The results of Western blot showed that relative expressions of β1-adrenergic receptor and β2-adrenergic receptor decreased in asphyxia group compared with normal group (all P<0.05). The relative expressions of β1-adrenergic receptor and β2-adrenergic receptor decreased in intervention group and asphyxia group compared with normal group on the 28th d (all P<0.05). The relative expressions of β1-adrenergic receptor and β2-adrenergic receptor had an ascending trend in intervention group compared with asphyxia group on the 28th d. HW/BW increased in asphyxia group compared with normal group, and decreased in intervention group compared with asphyxia group on the 28th d (all P<0.05).Conclusion In the development of immature myocardial cells, the expression of β1-adrenergic receptor increases and expression of β2-adrenergic receptor decreases in normal mice. Asphyxia will induce the decreases of expressions of β1-adrenergic receptor and β2-adrenergic receptor, and fenoterol pretreatment to specific β2-adrenoceptor agonist will improve the recovery of expressions of β1-adrenergic receptor and β2-adrenergic receptor.