Fu W J, Kuwahara M, Marumo F
Second Department of Internal Medicine, Tokyo Medical and Dental University, Japan.
Jpn J Physiol. 1995;45(1):97-109. doi: 10.2170/jjphysiol.45.97.
The mechanisms of cell volume regulation upon osmotic cell swelling were examined in the inner stripe of the outer medullary collecting duct (OMCDi). Segments of OMCDi were dissected from rabbit kidney and perfused in vitro. Using an image processing system, the cross-sectional area of tubule cells was monitored as an index of the relative cell volume. In response to a decrease in extracellular osmolality (290 to 190 mOsm), the tubule cells swelled promptly and restored gradually their original cell volume by a mechanism termed regulatory volume decrease (RVD). The initial response of RVD (the rate of the decrease in cell volume during the first 10 min) was inhibited by 79% at a high concentration of basolateral K+ (50 mM). By contrast, the same concentration of luminal K+ did not affect the response. When basolateral Cl- was removed 30 min before the experiment, the initial response of RVD was decreased by 77%, whereas the response was not affected 30 min after removal of luminal Cl-. Addition of basolateral Ba2+ and basolateral anthracene-9-CO2H inhibited the response by 70 and 65%, respectively. RVD response was accompanied by a transient rise in intracellular Ca2+. The Ca2+ rise was abolished when intracellular Ca2+ was chelated by acetoxymethyl ester of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM). In this condition, the initial RVD response was decreased by 68%. Our data suggest that the exit of basolateral K+ and Cl- via conductive pathways mainly mediates the RVD response in rabbit OMCDi cells, and that intracellular Ca2+ is involved in this response.
我们研究了外髓集合管内带（OMCDi）细胞在渗透性肿胀时的细胞容积调节机制。从兔肾中分离出OMCDi节段并进行体外灌注。使用图像处理系统，监测肾小管细胞的横截面积作为相对细胞容积的指标。响应细胞外渗透压降低（从290降至190 mOsm），肾小管细胞迅速肿胀，并通过一种称为调节性容积减小（RVD）的机制逐渐恢复其原始细胞容积。在高浓度基底外侧K⁺（50 mM）时，RVD的初始反应（最初10分钟内细胞容积减小的速率）受到79%的抑制。相比之下，相同浓度的管腔K⁺并不影响该反应。在实验前30分钟去除基底外侧Cl⁻时，RVD的初始反应降低了77%，而去除管腔Cl⁻ 30分钟后该反应不受影响。添加基底外侧Ba²⁺和基底外侧蒽-9-羧酸分别使反应受到70%和65%的抑制。RVD反应伴随着细胞内Ca²⁺的短暂升高。当细胞内Ca²⁺被1,2-双（2-氨基苯氧基）乙烷-N,N,N',N'-四乙酸乙酰氧甲酯（BAPTA-AM）螯合时，Ca²⁺升高被消除。在这种情况下，RVD的初始反应降低了68%。我们的数据表明，基底外侧K⁺和Cl⁻通过传导途径的外流主要介导了兔OMCDi细胞中的RVD反应，并且细胞内Ca²⁺参与了该反应。
