Avtor/Urednik		Kreft, Marko; Stenovec, Matjaž; Rupnik, Marjan; Grilc, Sonja; Kržan, Mojca; Potokar, Maja; Pangršič, Tina; Haydon, Philip G; Zorec, Robert
Naslov		Properties of Ca2+-dependent exocytosis in cultured astrocytes
Tip		članek
Vir		Glia
Vol. in št.		Letnik 46
Leto izdaje		2004
Obseg		str. 437-45
Jezik		eng
Abstrakt		Astrocytes, a subtype of glial cells, have numerous characteristics that were previously considered exclusive for neurons. One of these characteristics is a cytosolic [Ca2+] oscillation that controls the release of the chemical transmitter glutamate and atrial natriuretic peptide. These chemical messengers appear to be released from astrocytes via Ca2+-dependent exocytosis. In the present study, patch-clamp membrane capacitance measurements were used to monitor changes in the membrane area of a single astrocyte, while the photolysis of caged calcium compounds by a UV flash was used to elicit steps in [Ca2+]; to determine the exocytotic properties of astrocytes. Experiments show that astrocytes exhibit Ca2+-dependent increases in membrane capacitance, with an apparent Kd value of approx. 20 microM [Ca2+];. The delay between the flash delivery and the peak rate in membrane capacitance increase is in the range of tens to hundreds of milliseconds. The pretreatment of astrocytes by the tetanus neurotoxin, which specifically cleaves the neuronal/neuroendocrine type of SNARE protein synaptobrevin, abolished flash-induced membrane capacitance increases, suggesting that Ca2+-dependent membrane capacitance changes involve tetanus neurotoxin-sensitive SNARE-mediated vesicular exocytosis. Immunocytochemical experiments show distinct populations of vesicles containing glutamate and atrial natriuretic peptide in astrocytes. We conclude that the recorded Ca2+-dependent changes in membrane capacitance represent regulated exocytosis from multiple types of vesicles, about 100 times slower than the exocytotic response in neurons.
Deskriptorji		ASTROCYTES EXOCYTOSIS CALCIUM ATRIAL NATRIURETIC FACTOR GLUTAMATES ELECTRIC CONDUCTIVITY CELLS, CULTURED TETANUS TOXIN PATCH-CLAMP TECHNIQUES IMMUNOHISTOCHEMISTRY MICROSCOPY, CONFOCAL RATS