Effects of verapamil on down-regulation of norepinephrine-induced β adrenoceptors in cultured rat cardiomyocytes

目的：研究维拉帕米（Ｖｅｒ）是否能抑制去甲肾上腺素（ＮＥ）诱导的培养大鼠心肌细胞β受体下调及其可能机制．方法：β受体密度用［３Ｈ］ＤＮＡ放射配基标记法，细胞内游离钙用钙离子荧光探针Ｆｕｒａ２ＡＭ法测定．结果：Ｖｅｒ能明显降低培养大鼠心肌细胞内游离钙水平，增加β受体密度；ＮＥ增加细胞内游离钙水平，降低β受体密度；Ｖｅｒ能明显抑制ＮＥ引起的细胞内游离钙增加和β受体密度的降低．结论：Ｖｅｒ能增加正常心肌细胞β受体密度，抑制ＮＥ产生的心肌β受体下调．

AIM: To determine whether verapamil (Ver) inhibits norepinephrine (NE)induced β adrenoceptors downregulation in cultured rat cardiomyocytes. METHODS: Dihydroalprenolol (DHA) radiobinding assay was used to measure β adrenoceptor density, fluorescent indicator Fura 2AM was used to estimate levels of free cytosolic calcium ([Ca2+]i). RESULTS: Ver reduced [Ca2+]i and increased β adrenoceptor density, NE increased [Ca2+]i and reduced β adrenoceptor density of cultured cardiomyocytes, these effects were time and concentration dependent. Ver inhibited the above effects of NE. CONCLUSIONS: Ver increased β adrenoceptor density and inhibited NEinduced β adrenoceptor downregulation of cardiomyocytes.