Effects of metabolic acidosis on intracellular pH responses in multiple cell types

作者：Salameh Ahlam Ibrahim; Ruffin Vernon A; Boron Walter F^*

来源：American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, 2014, 307(12): R1413-R1427.

DOI：10.1152/ajpregu.00154.2014

• neurons
• astrocytes
• colon cancer
• skeletal muscle
• macrophages
• dendritic cells
• melanocytes
• keratinocytes

Metabolic acidosis (MAc), a decrease in extracellular pH (pH(o)) caused by a decrease in [HCO3-](o) at a fixed [CO2](o), is a common clinical condition and causes intracellular pH (pH(i)) to fall. Although previous work has suggested that MAc-induced decreases in pHi (Delta pH(i)) differ among cell types, what is not clear is the extent to which these differences are the result of the wide variety of methodologies employed by various investigators. In the present study, we evaluated the effects of two sequential MAc challenges (MAc1 and MAc2) on pHi in 10 cell types/lines: primary-cultured hippocampal (HCN) neurons and astrocytes (HCA), primary-cultured medullary raphe (MRN) neurons, and astrocytes (MRA), CT26 colon cancer, the C2C12 skeletal muscles, primary-cultured bone marrow-derived macrophages (BMDM) and dendritic cells (BMDC), Ink4a/ARF-null melanocytes, and XB-2 keratinocytes. We monitor pHi using ratiometric fluorescence imaging of 2%26apos;,7%26apos;-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein while imposing MAc: lowering (pHo) from 7.4 to 7.2 by decreasing [HCO3-] o from 22 to 14 mM at 5% CO2 for 7 min. After MAc1, we return cells to the control solution for 10 min and impose MAc2. Using our definition of MAc resistance [(Delta pH(i)/Delta pH(o)) %26lt;= 40%], during MAc1, similar to 70% of CT26 and similar to 50% of C2C12 are MAc-resistant, whereas the other cell types are predominantly MAc-sensitive. During MAc2, some cells adapt [(Delta pH(i)/Delta pH(o))(2) %26lt; (Delta pH(i)/Delta pH(o)) 1], particularly HCA, C2C12, and BMDC. Most maintain consistent responses [(Delta pH(i)/Delta pH(o))(2) %26gt; (Delta pH(i)/Delta pH(o))(1)], and a few decompensate [(Delta pH(i)/Delta pH(o))(2)%26gt;(Delta pH(i)/Delta pH(o))(1)], particularly HCN, C2C12, and XB-2. Thus, responses to twin MAc challenges depend both on the individual cell and cell type.

• 出版日期2014-12-15