Favus M J, Tembe V, Tanklefsky M D, Ambrosic K A, Nellans H N
Department of Medicine, University of Chicago, Illinois 60637.
Am J Physiol. 1989 Nov;257(5 Pt 1):G818-22. doi: 10.1152/ajpgi.1989.257.5.G818.
To determine the possible role of acidic lysosomal vesicles in the transcellular transport of Ca, bidirectional Ca fluxes were measured across intestinal segments in vitro in the absence of electrochemical gradients. Mucosal addition of the weak base quinacrine (0.2 mM) caused a 67% decline in the mucosal-to-serosal Ca flux (Jm----s) across duodenum (175 +/- 34 vs. 58 +/- 9 nmol.cm-2.h-1, P less than 0.007) and reduced cecal Ca Jm----s (177 +/- 15 vs. 45 +/- 4, P less than 0.0001). Higher concentrations of up to 2.0 mM caused no further decline in cecal Ca Jm----s. Inhibition of cecal Ca Jm----s by mucosal chloroquine (0.1 mM) or ammonium chloride (10 mM) varied from 37 to 50%. Addition in vitro of quinacrine to enterocyte basolateral membrane vesicles failed to inhibit ATP-dependent Ca uptake. The present studies demonstrate that agents that collapse lysosomal pH gradients inhibit transcellular Ca transport. These observations are consistent with the hypothesis that Ca destined for transcellular transport is functionally associated with acidic lysosomes and that these organelles play an important role in transepithelial Ca translocation.
为了确定酸性溶酶体囊泡在钙的跨细胞转运中的可能作用，在不存在电化学梯度的情况下，体外测量了跨肠段的双向钙通量。向黏膜添加弱碱喹吖因（0.2 mM）导致十二指肠黏膜到浆膜的钙通量（Jm→s）下降67%（175±34对58±9 nmol·cm-2·h-1，P<0.007），并降低了盲肠的钙Jm→s（177±15对45±4，P<0.0001）。高达2.0 mM的更高浓度并未导致盲肠钙Jm→s进一步下降。黏膜氯喹（0.1 mM）或氯化铵（10 mM）对盲肠钙Jm→s的抑制率在37%至50%之间。体外向肠上皮细胞基底外侧膜囊泡中添加喹吖因未能抑制ATP依赖性钙摄取。本研究表明，破坏溶酶体pH梯度的试剂会抑制跨细胞钙转运。这些观察结果与以下假设一致，即用于跨细胞转运的钙在功能上与酸性溶酶体相关，并且这些细胞器在跨上皮钙转运中起重要作用。
