【单选题】【消耗次数：1】
色甘酸钠预防哮喘发作的原理是
①
直接扩张支气管
②
抑制磷酸二酯酶，升高cAMP浓度
③
激动β2受体
④
阻断M受体
⑤
稳定肥大细胞膜，阻止炎性介质释放
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下列关于肥大细胞的描述，错误的是（）
①
细胞较大，呈圆形或椭圆形
②
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细胞质内充满嗜酸性颗粒，呈异染性
⑤
常沿小血管分布，参与机体的过敏反应
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