ATP stimulates calcium influx in primary astrocyte cultures

The effect of ATP and other purines on 45Ca uptake was studied in primary cultures of rat astrocytes. Treatment of the cells with ATP for 1 to 30 min brought about an increase in cellular 45Ca. Stimulation of calcium influx by ATP was investigated using a 90 sec exposure to 45Ca and over a concentration range of 0.1 nM to 3 mM; a biphasic dose-response curve was obtained with EC 50 values of 0.3 nM and 9 uM, indicating the presence of low and high affinity purinergic binding sites. Similar levels of 45Ca influx at 90 sec were observed with ATP, ADP and adenosine (all at 100 uM). Prior treatment of the cultures with LaCl 3 blocked the purine-induced 45Ca influx. These findings indicate that one pathway for calcium entry in astrocytes involves purinergic receptor-operated, calcium channels.