Moran A, Montrose M H, Murer H
Department of Physiology, Corob Center for Medical Research, Faculty of Health Sciences, Ben-Gurion University, Negev, Beer-Sheva, Israel.
Biochim Biophys Acta. 1988 Apr 2;969(1):48-56. doi: 10.1016/0167-4889(88)90087-0.
The activity of Na+-H+, exchange was studied in a cultured cell line derived from opossum kidney (OK cells). The activity of the exchanger was measured either as the amiloride (2 mM) inhibitable 22Na flux in acid-loaded cells, or as the Na+-dependent and amiloride-sensitive recovery of intracellular pH (pHi) from an acid load. Initial rates of tracer flux were analyzed in confluent monolayers while changes in pHi were evaluated in suspensions of trypsinized cells which had been loaded with 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein. Both 8-bromo-cAMP and 8-bromo-cGMP inhibit the activity of the exchanger in a dose-dependent manner. Maximal inhibition due to 8-bromo-cAMP was about 50% and was attained with 0.75 mM of the cyclic nucleotide. Parathyroid hormone (10(-9)-10(-7) M) and atrial natriuretic peptide (10(-7) M) also inhibit the activity of the exchanger. By measuring the rate of Na+-dependent pHi recovery from different starting pHi values, evidence was obtained for a cyclic nucleotide-dependent decrease in the response of Na+-H+ exchange to intracellular acidification. We conclude that cAMP and cGMP are intracellular messengers in the hormone-dependent regulation of Na+-H+ exchange activity in renal epithelial cells.
在源自负鼠肾的培养细胞系（OK细胞）中研究了Na⁺-H⁺交换活性。交换体活性的测定方法有两种：一是在酸负荷细胞中测定阿米洛利（2 mM）可抑制的²²Na通量；二是测定从酸负荷状态下细胞内pH（pHi）的Na⁺依赖性且对阿米洛利敏感的恢复情况。在汇合的单层细胞中分析示踪剂通量的初始速率，而在已用2',7'-双（2-羧乙基）-5,6-羧基荧光素加载的胰蛋白酶消化细胞悬液中评估pHi的变化。8-溴-cAMP和8-溴-cGMP均以剂量依赖性方式抑制交换体的活性。8-溴-cAMP引起的最大抑制约为50%，在0.75 mM的环核苷酸时达到该抑制水平。甲状旁腺激素（10⁻⁹ - 10⁻⁷ M）和心房利钠肽（10⁻⁷ M）也抑制交换体的活性。通过测量从不同起始pHi值开始的Na⁺依赖性pHi恢复速率，获得了证据表明环核苷酸依赖性地降低了Na⁺-H⁺交换对细胞内酸化的反应。我们得出结论，cAMP和cGMP是肾上皮细胞中激素依赖性调节Na⁺-H⁺交换活性的细胞内信使。
