Bachmann Oliver, Heinzmann Alexander, Mack Andreas, Manns Michael P, Seidler Ursula
Department of Gastroenterology, Hepatology, and Endocrinology, Hannover Medical School, Hannover, Germany.
Am J Physiol Gastrointest Liver Physiol. 2007 Mar;292(3):G711-7. doi: 10.1152/ajpgi.00416.2006. Epub 2006 Nov 9.
We have previously shown that stimulation of acid secretion in parietal cells causes rapid initial cell shrinkage, followed by Na(+)/H(+) exchange-mediated regulatory volume increase (RVI). The factors leading to the initial cell shrinkage are unknown. We therefore monitored volume changes in cultured rabbit parietal cells by confocal measurement of the cytoplasmic calcein concentration. Although blocking the presumably apically located K(+) channel KCNQ1 with chromanol 293b reduced both the forskolin- and carbachol-induced cell shrinkage, inhibition of Ca(2+)-sensitive K(+) channels with charybdotoxin strongly inhibited the cell volume decrease after carbachol, but not after forskolin stimulation. The cell shrinkage induced by both secretagogues was partially inhibited by blocking H(+)-K(+)-ATPase with SCH28080 and completely absent after incubation with NPPB, which inhibits parietal cell anion conductances involved in acid secretion. The subsequent RVI was strongly inhibited with the Na(+)/H(+) exchanger 1 (NHE1)-specific concentration of HOE642 and completely by 500 muM dimethyl-amiloride (DMA), which also inhibits NHE4. None of the above substances induced volume changes under baseline conditions. Our results indicate that cell volume decrease associated with acid secretion is dependent on the activation of K(+) and Cl(-) channels by the respective secretagogues. K(+), Cl(-), and water secretion into the secretory canaliculi is thus one likely mechanism of stimulation-associated cell shrinkage in cultured parietal cells. The observed RVI is predominantly mediated by NHE1.
我们之前已经表明，壁细胞中酸分泌的刺激会导致细胞迅速出现初始收缩，随后是由Na(+)/H(+)交换介导的调节性容积增加（RVI）。导致初始细胞收缩的因素尚不清楚。因此，我们通过共聚焦测量细胞质钙黄绿素浓度来监测培养的兔壁细胞中的容积变化。尽管用色满醇293b阻断可能位于顶端的钾通道KCNQ1可减少福斯高林和卡巴胆碱诱导的细胞收缩，但用蝎毒素抑制钙敏感钾通道可强烈抑制卡巴胆碱刺激后细胞容积的减小，但对福斯高林刺激后则无此作用。两种促分泌剂诱导的细胞收缩均被SCH28080阻断H(+)-K(+)-ATP酶部分抑制，而在用NPPB孵育后则完全消失，NPPB可抑制参与酸分泌的壁细胞阴离子电导。随后的RVI被Na(+)/H(+)交换体1（NHE1）特异性浓度的HOE642强烈抑制，而被500 μM二甲基氨氯吡脒（DMA）完全抑制，DMA也抑制NHE。上述物质在基线条件下均未引起容积变化。我们的结果表明，与酸分泌相关的细胞容积减小取决于各自促分泌剂对钾通道和氯通道的激活。钾离子、氯离子和水分泌到分泌小管中因此可能是培养的壁细胞中与刺激相关的细胞收缩的一种机制。观察到的RVI主要由NHE1介导。
