HCO3刺激的ATP酶在缓冲物质转运中的作用。

The role of HCO3-stimulated ATPase in buffer transport.

作者信息

Wais U, Knauf H

出版信息

Curr Probl Clin Biochem. 1976;6:154-61.

PMID:11963

Abstract

An ATPase stimulated by HCO-3ions and other oxybases and inhibited by SCN- has been found in main excretory duct of rat submaxillary gland, a tissue, capable of actively secreting HCO-3ions. No such ATPase was found in the rabbit duct, which normally does not secrete HCO-3. The HCO-3ATPase was localized in the plasma membrane fraction of the homogenate, as evidenced by the marker 5'nucleotidase. The activities of the HCO-3ATPase increased in metabolic alkalosis and decreased in metabolic acidosis in parallel to secretion of HCO-3 and K+ ions by the rat salivary duct epithelium. In renal cortex tissue, where HCO-3 is actively reabsorbed respectively H+ is secreted, there was also found a parallel change in the activity of the HCO-3ATPase and the rate of active H+ secretion. These findings provide further evidence that the membrane-bound HCO-3ATPase is involved in active H+/HCO-3 transport. The HCO-3ATPase is not only stimulated by HCO-3 but also by other non transportable oxybases, a finding which indicates H+ rather than HCO-3 being the actively transported component of the buffer system. Small concentrations of K+ ions decrease the Km for HCO-3 and thus yield stimulation of the HCO-3-ATPase. Thport changing in parallel with that of H+/HCO-3 may be taken as indicative for a coupled K+-H+-exchange mechanism to which the HCO-3ATPase is linked.

摘要

在大鼠下颌下腺的主排泄管中发现了一种受HCO₃⁻离子和其他含氧碱刺激并受SCN⁻抑制的ATP酶，该组织能够主动分泌HCO₃⁻离子。在兔的导管中未发现这种ATP酶，兔导管通常不分泌HCO₃⁻。HCO₃⁻ATP酶定位于匀浆的质膜部分，5'-核苷酸酶标记可证明这一点。大鼠唾液导管上皮分泌HCO₃⁻和K⁺离子时，HCO₃⁻ATP酶的活性在代谢性碱中毒时增加，在代谢性酸中毒时降低。在肾皮质组织中，HCO₃⁻被主动重吸收而H⁺被分泌，HCO₃⁻ATP酶的活性和主动分泌H⁺的速率也有类似变化。这些发现进一步证明膜结合的HCO₃⁻ATP酶参与了H⁺/HCO₃⁻的主动转运。HCO₃⁻ATP酶不仅受HCO₃⁻刺激，也受其他不可转运的含氧碱刺激，这一发现表明H⁺而非HCO₃⁻是缓冲系统的主动转运成分。低浓度的K⁺离子降低了HCO₃⁻的Km值，从而刺激了HCO₃⁻-ATP酶。与H⁺/HCO₃⁻转运平行变化的转运可能表明存在一种与HCO₃⁻ATP酶相关的K⁺-H⁺交换偶联机制。