Author/Editor		Pangršič, Tina; Potokar, Maja; Haydon, Philip G; Zorec, Robert; Kreft, Marko
Title		Astrocyte swelling leads to membrane unfolding, not membrane insertion
Type		članek
Source		J Neurochem
Vol. and No.		Letnik 99, št. 2
Publication year		2006
Volume		str. 514-23
Language		eng
Abstract		The mechanisms mediating the release of chemical transmitters from astrocytes are the subject of intense research. Recent experiments have shown that hypotonic conditions stimulate the release of glutamate and ATP from astrocytes, but a mechanistic understanding of this process is not available. To determine whether hypotonicity activates the process of regulated exocytosis, we monitored membrane capacitance by the whole-cell patch-clamp technique whilst a hypotonic medium was applied to cultured astrocytes. If exocytosis is triggered under hypotonic conditions, as it is following increases in cytosolic calcium, a net increase in membrane surface area, monitored by measuring the whole-cell membrane capacitance, is expected. Simultaneous measurements of cell size and whole-cell membrane conductance and surface area demonstrated that hypotonic medium (210 mOsm for 200 s) resulted in an increase in membrane conductance and in the swelling of cultured astrocytes by an average of 40%, as monitored by cell cross-sectional area, but without any corresponding change in membrane surtace area. As we have demonstrated that capacitance measurements have the sensitivity to detect increases in cell surface area as small as 0.5%, we conclude that cell swelling occurs via an exocytosisindependent mechanism, probably involving the unfolding of the plasma membrane.
Descriptors		ASTROCYTES EXOCYTOSIS CALCIUM HYPOTONIC SOLUTIONS CELL SIZE PATCH-CLAMP TECHNIQUES ELECTRIC CONDUCTIVITY MICROSCOPY, CONFOCAL RATS, WISTAR