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首页> 外文期刊>American Journal of Physiology >Effects of extracellular calcium and potassium on the sodium pump of rat adrenal glomerulosa cells.
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Effects of extracellular calcium and potassium on the sodium pump of rat adrenal glomerulosa cells.

机译：细胞外钙和钾对大鼠肾上腺肾小球细胞钠泵的影响。

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Because the activity of the sodium pump (Na-K-ATPase) influences the secretion of aldosterone, we determined how extracellular potassium (K(o)) and calcium affect sodium pump activity in rat adrenal glomerulosa cells. Sodium pump activity was measured as ouabain-sensitive (86)Rb uptake in freshly dispersed cells containing 20 mM sodium as measured with sodium-binding benzofluran isophthalate. Increasing K(o) from 4 to 10 mM in the presence of 1.8 mM extracellular calcium (Ca(o)) stimulated sodium pump activity up to 165% and increased intracellular free calcium as measured with fura 2. Increasing K(o) from 4 to 10 mM in the absence of Ca(o) stimulated the sodium pump approximately 30% and did not increase intracellular free calcium concentration ([Ca(2+)](i)). In some experiments, addition of 1.8 mM Ca(o) in the presence of 4 mM K(o) increased [Ca(2+)](i) above the levels observed in the absence of Ca(o) and stimulated the sodium pump up to 100%. Ca-dependent stimulation of the sodium pump by K(o) and Ca(o) was inhibited by isradipine (10 microM), a blocker of L- and T-type calcium channels, by compound 48/80 (40 microg/ml) and calmidizolium (10 microM), which inhibits calmodulin (CaM), and by KN-62 (10 microM), which blocks some forms of Ca/CaM kinase II (CaMKII). Staurosporine (1 microM), which effectively blocks most forms of protein kinase C, had no effect. In the presence of A-23187, a calcium ionophore, the addition of 0.1 mM Ca(o) increased [Ca(2+)](i) to the level observed in the presence of 10 mM K(o) and 1.8 mM Ca(o) and stimulated the sodium pump 100%. Ca-dependent stimulation by A-23187 and 0.1 mM Ca(o) was not reduced by isradipine but was blocked by KN-62. Thus, under the conditions that K(o) stimulates aldosterone secretion, it stimulates the sodium pump by two mechanisms: direct binding to the pump and by increasing calcium influx, which is dependent on Ca(o). The resulting increase in [Ca(2+)](i) may stimulate the sodium pump by activating CaM and/or CaMKII.
机译：因为钠泵的活性（Na-K​​-ATPase）影响醛固酮的分泌，所以我们确定了细胞外钾（K（o））和钙如何影响大鼠肾上腺肾小球细胞钠泵的活性。钠泵活性的测量是在含有20 mM钠的新鲜分散细胞中对哇巴因敏感的（86）Rb摄取，用与钠结合的苯甲氟醚间苯二酸酯测量。如呋喃2所测，在存在1.8 mM细胞外钙（Ca（o））的情况下将K（o）从4增加到10 mM刺激钠泵活性高达165％，并增加细胞内游离钙。 Ca（o）不存在的情况下，最大10 mM刺激钠泵约30％，并且不增加细胞内游离钙浓度（[Ca（2 +）]（i））。在某些实验中，在存在4 mM K（o）的情况下添加1.8 mM Ca（o）使[Ca（2 +）]（i）高于在没有Ca（o）的情况下观察到的水平，并刺激了钠泵高达100％。化合物48/80（40 microg / ml）抑制了伊拉地平（10 microM）（一种L和T型钙通道的阻滞剂）抑制了K（o）和Ca（o）对钠泵的钙依赖性刺激。抑制钙调蛋白（CaM）的Calidizolium（10 microM），以及阻断某些形式的Ca / CaM激酶II（CaMKII）的KN-62（10 microM）。 Staurosporine（1 microM）有效阻止大多数形式的蛋白激酶C，但没有作用。在钙离子载体A-23187的存在下，添加0.1 mM Ca（o）使[Ca（2 +）]（i）增至在10 mM K（o）和1.8 mM Ca的存在下观察到的水平（o）并刺激钠泵100％。依地平未降低A-23187和0.1 mM Ca（o）的钙依赖性刺激，但被KN-62阻断。因此，在K（o）刺激醛固酮分泌的条件下，它通过两种机制刺激钠泵：直接结合至泵和通过增加钙流（取决于Ca（o））。 [Ca（2 +）]（i）的增加可能会通过激活CaM和/或CaMKII刺激钠泵。

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