Marcos Morales M, Purchio Brucoli H C, Malnic G, Gil Lopes A
Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil.
Mol Cell Biochem. 1996 Jan 12;154(1):17-21. doi: 10.1007/BF00248456.
Renal tubule acidification was studied in thyroparathyroidectomized rats which had the parathyroids reimplanted into cervical muscle tissue, by stopped-flow microperfusion using ion-exchange resin microelectrodes. Hypothyroid rats had decreased rates of proximal and late distal bicarbonate reabsorption. This reduction occurred in the absence of changes in pH gradients, and was due mostly to decreases in acidification half-times, that is, of the rate of bicarbonate exit from the tubule lumen. H+ back-flux from the lumen measured during luminal perfusion with solutions at pH 6 (below stationary pH) was decreased in proximal tubule of hypothyroid rats, showing that the acidification defect was not due to an increased H+ shunt across the epithelium. These data indicate that in hypothyroid rats the proximal tubule luminal density of Na+/H+ exchangers or their turnover is decreased in the absence of alterations in the driving force (H+ and Na+ gradients across the luminal membrane) for H+ secretion. The effect observed in distal tubule may be due to action on Na+/H+ exchangers that are present also on this site, or to an impairment of the action of other H+ transporters such as H(+)-ATPases, including the provision of energy for them. 9
通过使用离子交换树脂微电极的停流微灌注技术，对甲状旁腺移植到颈部肌肉组织的甲状旁腺切除大鼠的肾小管酸化进行了研究。甲状腺功能减退大鼠近端和远端晚期碳酸氢盐重吸收率降低。这种降低在pH梯度无变化的情况下发生，主要是由于酸化半衰期缩短，即碳酸氢盐从肾小管腔排出的速率降低。在用pH 6（低于稳定pH）的溶液进行管腔灌注期间，甲状腺功能减退大鼠近端小管中从管腔测量的H+回流减少，表明酸化缺陷不是由于跨上皮的H+分流增加。这些数据表明，在甲状腺功能减退大鼠中，在H+分泌的驱动力（跨管腔膜的H+和Na+梯度）无改变的情况下，近端小管Na+/H+交换体的管腔密度或其周转率降低。在远端小管观察到的效应可能是由于作用于该部位也存在的Na+/H+交换体，或由于其他H+转运体（如H(+)-ATP酶）的作用受损，包括为它们提供能量。 9
