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Calcium ionophore-induced changes in HCO3- secretion and Cl- absorption in turtle bladder: relation to action of 3-isobutyl-1-methylxanthine.

Authors
Type
Published Article
Journal
Biochimica et Biophysica Acta
0006-3002
Publisher
Elsevier
Publication Date
Volume
900
Issue
1
Pages
56–62
Identifiers
PMID: 2439120
Source
Medline
License
Unknown

Abstract

The calcium ionophore A23187 stimulates luminal alkalinization and inhibits Cl- absorption in short-circuited urinary bladders of postprandial or alkalotic turtles. The ionophore appears to mimic the action of the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX) by its similar effects on HCO3- secretion and Cl- absorption and by increasing cytosolic cAMP levels of isolated bladder epithelial cells. However, only A23187 (or ionomycin), but not IMBX or cAMP, elevated cytosolic Ca2+ of aequorin- or quin2-loaded cells. Since A23187, but not IBMX or cAMP inhibits luminal acidification, we postulate that cytosolic Ca2+ regulates the acidification process by a cAMP-independent mechanism and controls HCO3- secretion as well as Cl- absorption, at least in part, via cAMP-mediated pathways.

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