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Bethanechol inhibition of chicken intestinal brush border Na/H exchange: Role of protein kinase C and other calcium‐dependent processes
Author(s) -
Musch Mark W.,
DrabikArvans Donna,
Rao Mrinalini C.,
Chang Eugene B.
Publication year - 1992
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041520218
Subject(s) - bethanechol , ionomycin , enterocyte , calcium , brush border , chemistry , protein kinase c , biophysics , protein kinase a , biochemistry , biology , intracellular , small intestine , vesicle , kinase , membrane , muscarinic acetylcholine receptor , receptor , organic chemistry
Bethanechol, a muscarinic agonist, inhibits the initial rate of amiloride‐sensitive Na uptake by intact mucosa of avian small intestine as well as by isolated chicken villus enterocytes, an effect that is maximal at 90 seconds and reverses by 6 minutes. Bethanechol similarly decreases intracellular pH in isolated cells suspended in bicarbonate‐free buffer in a time course similar to inhibition of enterocyte Na uptake, suggesting inhibition of Na/H exchange. In brush border membrane vesicles rapidly prepared from cells stimulated with bethanechol, proton‐dependent 22 Na uptake is transiently inhibited in a time course similar to inhibition of cell Na uptake. Bethanechol also stimulates transient translocation of protein kinase C from the cytosol to the particulate fraction, a portion of this activity translocating to the brush border membrane. To determine the calcium dependence of bethanechol's action, enterocytes were loaded with varying concentrations of the calcium buffering agent quin‐2. Inhibition of cell Na uptake by the calcium ionophore ionomycin could be completely reversed by quin‐2 buffering in a concentration‐dependent manner. In contrast, quin‐2 buffering had little or no effect on the inhibition of Na uptake caused by the protein kinase C activators phorbol esters and oleoylacetylglycerol. Bethanechol's inhibitory effects were partially, but not completely reversed by quin‐2 buffering. These data suggest that the effects of bethanechol on chicken villus enterocyte brush border Na/H exchange are mediated by calcium‐dependent process(es) as well as by protein kinase C. © 1992 Wiley‐Liss, Inc.