AGONIST-INDUCED CA2-CELLS AND ASTROCYTES - A COMPARATIVE-STUDY( TRANSIENTS IN CULTURED RAT ENTERIC GLIAL)

Background: Enteric glial cells show morphological similarities to ast rocytes, but little is known about their regulation. Methods: The effe cts of various agonists on intracellular Ca2+ were studied by means of fura-2 fluorescence at the single-cell level in cultured rat enteric glial cells and primary rat astrocytes. Results: Both cell types stain ed positive for glutamine synthetase, S-100, and glial fibrillary acid ic protein, and rapid elevations of intracellular Ca2+ were observed i n response to endothelin-1, extracellular adenosine 5'-triphosphate, u ridine 5'-triphosphate, and vasopressin. In enteroglia, endothelin-1 i nduced a calcium signal different from that evoked in astrocytes. In c ontrast to astrocytes, enteroglia did not show an increase of intracel lular Ca2+ following addition of angiotensin II, bradykinin, a-adrener gic agonists, carbachol, prostaglandin E-2, glutamate, dopamine, epide rmal growth factor, substance P, or neurokinins, and only 5-15% of the enteroglial cells responded to serotonin, histamine, epinephrine, and prostaglandin F-2 alpha. Hypoosmotic exposure led to a rapid increase of intracellular Ca2+ concentration followed by a sustained plateau i n astrocytes. In enteroglia, hypoosmolarity did not evoke an initial C a2+ spike, but led to a slow increase of intracellular Ca2+, due to in flux from the extracellular space. Conclusion: There are marked differ ences between enteroglia and brain astrocytes with respect to their re gulation by calcium-mobilizing agonists and hypoosmolarity.