INTERACTION OF NH4+ AND LI+ WITH THE RENAL MICROVILLUS MEMBRANE NA+-H+ EXCHANGER
INTERACTION OF NH4+ AND LI+ WITH THE RENAL MICROVILLUS MEMBRANE NA+-H+ EXCHANGER
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DOI：
10.1152/ajpcell.1981.241.5.c220
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发表时间：
1981-01-01
影响因子：
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通讯作者：
ARONSON, PS
中科院分区：
文献类型：
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作者：
KINSELLA, JL;ARONSON, PS
在兔肾微绒毛膜囊泡中，研究了NH_4~+、Li~+与Na~+-H~+交换器的相互作用。[14C]DMO[5，5-二甲基恶唑烷-2，4-二酮]摄取通过流动透析监测囊泡内间隙的碱化，这是由于在外部介质中加入Na+、Li+或NH4+的Cl-盐所致。用快速过滤技术测定的22Na+摄取速率与外界Na+浓度(KT 6 mM Na+)是饱和的，并被外部Li+(KI 1.9 mM)和NH4+(KI 4.3 mM)竞争性抑制。外源Na+和NH4+可促进预先加载Na+的囊泡~(22)Na+外流，而外源Li+则抑制外源Na~+外流。显然，肾微绒毛膜Na+-H+交换器对Li+和NH4+具有亲和力，不仅可以调节Na+对H+的交换，还可以调节Na+对Na+的交换，Na+对NH4+的交换，Li+对H+的交换，可能还有Li+对Na+的交换。Na+-H+交换以外的其他交换方式的生理意义尚不确定，但Na+-NH4+交换可能在近端肾小管酸化过程中发挥作用。
The interaction of NH4+ and Li+ with the Na+-H+ exchanger was studied in rabbit renal microvillus membrane vesicles. Alkalinization of the intravesicular space, monitored with [14C]DMO [5,5-dimethoxazolidine-2,4-dione] uptake by flow dialysis, resulted from the addition of Cl- salts of Na+, Li+ or NH4+ to the external medium. The 22Na+ uptake rate, assayed by a rapid filtration technique, was saturable with respect to external Na+ concentration (KT 6 mM Na+) and was competitively inhibited by external Li+ (Ki 1.9 mM) and NH4+ (Ki 4.3 mM). Efflux of 22Na+ from vesicles preloaded with Na+ was stimulated by external Na+ and NH4+ but inhibited by external Li+. Apparently, the renal microvillus membrane Na+-H+ exchanger has affinity for Li+ and NH4+ and can mediate the exchange not only of Na+ for H+ but also of Na+ for Na+, Na+ for NH4+, Li+ for H+ possibly NH4+ for H+, and perhaps Li+ for Na+. The physiological significance of exchange modes other than Na+-H+ exchange is uncertain, but Na+-NH4+ exchange could play a role in the proximal tubular acidification process.