Morphological and functional coupling of IP3 receptors with Na pumps in adrenal chromaffin cells

肾上腺染色质细胞暴露于高浓度的皮质激素，其中一种是乌阿拜样物质。因此，我们采用电流法和免疫细胞化学检测了乌阿巴因对嗜铬细胞中儿茶酚胺分泌和Na^+、K^+- atp酶α亚基分布的影响。虽然暴露于1 μM瓦巴因对分泌没有明显影响，但由于部分储存的Ca^<2+>被动员，导致分泌增加。免疫细胞化学显示Na^+， K^+- atp酶α1亚单位样免疫反应性（IR）普遍分布于细胞外周，α2样免疫反应性存在于部分细胞外周。肌醇三磷酸受体（InsP_3R） 2型样IR分布在核周和质膜附近，与BODIPY-FL-InsP_3结合一致。外周BODIPY-FL-InsP_3结合位点位于α2样IR膜下，表明外周含有Ca^<2+>的InsP_3R型2存储与α2亚基的膜并置。这种密切的联系可能解释了在1 μM瓦巴因的存在下，Ca^<2+>被吸收到储存中并随之增加动员依赖性分泌的原因。

Adrenal chromaffin cells are exposed to high concentrations of cortical hormones, one of which is ouabain-like substance. Thus, the effects of ouabain on catecholamine secretion and distribution of Na^+, K^+-ATPase α subunits in chromaffin cells were examined using amperometry and immunocytochemistry. While exposure to 1 μM ouabain did not have a marked effect on resulting secretion, it induced an increase in the secretion due to mobilization of partially stored Ca^<2+>. Immunocytochemistry revealed that Na^+, K^+-ATPase α1 subunit-like immunoreactivity (IR) was distributed ubiquitously at cell periphery, whereas α2-like IR were present at part of cell periphery. Inositol trisphosphate receptor (InsP_3R) type 2-like IR was distributed perinuclearly and in the vicinity of the plasma membrane, consistent with that of BODIPY-FL-InsP_3 binding. Peripheral BODIPY-FL-InsP_3 binding sites underlay membranes with α2-like IR, indicating that the peripheral InsP_3R type 2-containing Ca^<2+> storage was juxtaposed to membranes with the α2 subunit. This close association may account for the facilitation of Ca^<2+> uptake into stores and the consequent increase in mobilization-dependent secretion in the presence of 1 μM ouabain.