Journal
AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY
Volume 281, Issue 5, Pages C1533-C1541Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpcell.2001.281.5.C1533
Keywords
SGLT1; p38 mitogen-activated protein kinase; nutrient absorption; Na+/H+ exchanger isoform 3
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Funding
- NIDDK NIH HHS [DK-02503, DK-56121, R01 DK061931-01] Funding Source: Medline
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Cytoplasmic pH (pH(i)) was evaluated during Na+-glucose cotransport in Caco-2 intestinal epithelial cell monolayers. The pH(i) increased by 0.069 +/- 0.002 within 150 s after initiation of Na+-glucose cotransport. This increase occurred in parallel with glucose uptake and required expression of the intestinal Na+-glucose cotransporter SGLT1. S-3226, a preferential inhibitor of Na+/H+ exchanger (NHE) isoform 3 (NHE3), prevented cytoplasmic alkalinization after initiation of Na+-glucose cotransport with an ED50 of 0.35 muM, consistent with inhibition of NHE3, but not NHE1 or NHE2. In contrast, HOE-694, a poor NHE3 inhibitor, failed to significantly inhibit pH(i) increases at <500 M. Na+-glucose cotransport was also associated with activation of p38 mitogen-activated protein (MAP) kinase, and the p38 MAP kinase inhibitors PD-169316 and SB-202190 prevented pH(i) increases by 100 +/- 0.1 and 86 +/- 0.1%, respectively. Conversely, activation of p38 MAP kinase with anisomycin induced NHE3-dependent cytoplasmic alkalinization in the absence of Na+-glucose cotransport. These data show that NHE3-dependent cytoplasmic alkalinization occurs after initiation of SGLT1-mediated Na+-glucose cotransport and that the mechanism of this NHE3 activation requires p38 MAP kinase activity. This coordinated regulation of glucose (SGLT1) and Na+ (NHE3) absorptive processes may represent a functional activation of absorptive enterocytes by luminal nutrients.
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