Milton A E, Weiner I D
Division of Nephrology, Hypertension and Transplantation, University of Florida College of Medicine, Gainesville 32610, USA.
Am J Physiol. 1997 Sep;273(3 Pt 2):F340-7. doi: 10.1152/ajprenal.1997.273.3.F340.
The A cell may possess multiple H+ transporters, including H(+)-adenosinetriphosphatase (H(+)-ATPase) and H(+)-K(+)-ATPase. The current study examines the relative roles of proton transporters in the A cell by observing their contribution to both basal intracellular pH (pHi) regulation and pHi recovery from an intracellular acid load. CCD were studied using in vitro microperfusion, and pHi was measured in the individual A cell using the fluorescent, pH-sensitive dye, 2',7'-bis(carboxyethyl)-5(6)-carboxy-fluorescein (BCECF). Inhibiting H(+)-ATPase with luminal bafilomycin A1 decreased basal pHi, whereas inhibiting apical H(+)-K(+)-ATPase with either luminal Sch-28080 or luminal potassium removal did not. The predominant mechanism of pHi, recovery from an intracellular acid load was peritubular sodium dependent and peritubular ethylisopropylamiloride (EIPA) sensitive, identifying basolateral Na+/H+ exchange activity. In the absence of peritubular sodium, pHi recovery was inhibited by luminal bafilomycin A1 but not by luminal Sch-28080 addition or by luminal potassium removal. However, when Na+/H+ exchange was inhibited with EIPA, both bafilomycin A1 sensitive and potassium dependent, Sch-28080-sensitive components of pHi recovery were present. Quantitatively, the rate of H(+)-ATPase proton secretion was greater than the rate of H(+)-K(+)-ATPase proton secretion. We conclude that basolateral Na+/H+ exchange is the predominant mechanism of A cell pHi recovery from an intracellular acid load. An apical H(+)-ATPase is the primary apical transporter contributing to A cell pHi regulation. An apical H(+)-K(+)-ATPase, while present, plays a more limited role under the conditions tested.
A细胞可能拥有多种H⁺转运体，包括H⁺ - 三磷酸腺苷酶（H⁺ - ATP酶）和H⁺ - K⁺ - ATP酶。本研究通过观察质子转运体对基础细胞内pH（pHi）调节以及从细胞内酸负荷中恢复pHi的贡献，来研究质子转运体在A细胞中的相对作用。使用体外微灌注研究皮质集合管（CCD），并使用荧光pH敏感染料2',7'-双（羧乙基）-5（6）-羧基荧光素（BCECF）在单个A细胞中测量pHi。用管腔巴弗洛霉素A1抑制H⁺ - ATP酶会降低基础pHi，而用管腔Sch - 28080或去除管腔钾抑制顶端H⁺ - K⁺ - ATP酶则不会。从细胞内酸负荷中恢复pHi的主要机制是依赖于管周钠且对管周乙基异丙基amiloride（EIPA）敏感，这表明存在基底外侧Na⁺/H⁺交换活性。在没有管周钠的情况下，管腔巴弗洛霉素A1会抑制pHi恢复，但添加管腔Sch - 28080或去除管腔钾则不会。然而，当用EIPA抑制Na⁺/H⁺交换时，pHi恢复中存在对巴弗洛霉素A1敏感和依赖钾以及对Sch - 28080敏感的成分。从数量上看，H⁺ - ATP酶质子分泌速率大于H⁺ - K⁺ - ATP酶质子分泌速率。我们得出结论，基底外侧Na⁺/H⁺交换是A细胞从细胞内酸负荷中恢复pHi的主要机制。顶端H⁺ - ATP酶是对A细胞pHi调节起主要作用的顶端转运体。顶端H⁺ - K⁺ - ATP酶虽然存在，但在所测试的条件下起的作用更有限。
