Sabatini S, Kurtzman N A
Miner Electrolyte Metab. 1985;11(4):277-80.
Despite 100% reabsorption of renal carbonic anhydrase activity, 70% of filtered bicarbonate is still reabsorbed. Recent data suggest that one of the mechanisms mediating carbonic anhydrase-independent bicarbonate reabsorption is the generation of favorable concentration gradients across the distal nephron following inhibition of carbonic anhydrase activity. Additional work suggests that the generation of favorable voltage gradients across the cortical collecting tubule may also mediate carbonic anhydrase-independent bicarbonate reabsorption. These studies were performed in turtle bladder to examine this issue. Acidification in this membrane was measured over a range of mucosa-negative potential difference of from 0 to 100 mV in the presence and absence of carbonic anhydrase activity. Under both conditions there was a linear increase in acidification as the potential difference increased. The rate of increase, however, was slightly less than 50% in the bladders subjected to carbonic anhydrase inhibition as compared to those with intact carbonic anhydrase activity. These data demonstrate that favorable electrical gradients enhance carbonic anhydrase-independent acidification as do favorable concentration gradients. We suggest that carbonic anhydrase-independent bicarbonate reabsorption in the kidney is mediated by a combination of favorable concentration and electrical gradients.
尽管肾脏碳酸酐酶活性的重吸收率达100%，但滤过的碳酸氢盐仍有70%被重吸收。最近的数据表明，介导非碳酸酐酶依赖性碳酸氢盐重吸收的机制之一是在碳酸酐酶活性受到抑制后，在远端肾单位产生有利的浓度梯度。更多研究表明，在皮质集合管产生有利的电压梯度也可能介导非碳酸酐酶依赖性碳酸氢盐重吸收。这些研究是在龟膀胱中进行的，以探讨这个问题。在有和没有碳酸酐酶活性的情况下，在0至100 mV的一系列黏膜负电位差范围内测量该膜的酸化情况。在这两种情况下，随着电位差增加，酸化呈线性增加。然而，与碳酸酐酶活性完整的膀胱相比，受到碳酸酐酶抑制的膀胱中酸化增加速率略低于50%。这些数据表明，有利的电势梯度与有利的浓度梯度一样，会增强非碳酸酐酶依赖性酸化。我们认为，肾脏中不依赖碳酸酐酶的碳酸氢盐重吸收是由有利的浓度梯度和电势梯度共同介导的。
