PURINERGIC (P(2)) RECEPTOR-OPERATED CALCIUM-ENTRY INTO RAT-THYROID CELLS

In the epithelial cell line FRT, derived from rat thyroid, extracellular ATP, at a concentration as low as 1×10−7 M, specifically increases cytosolic Ca++ two fold over the basal level of 255±45 nM. A maximum increase of 5 fold over basal is seen at 1×10−5 M ATP. The effect occurs in the absence of any measurable phosphatidyl inositol metabolism and requires the presence of extracellular Ca++ but is independent of extracellular Na+ it is duplicated by ATPγS but not by adenosine, AMP, ADP, AMP-PNP, AMP-CPP, or AMP-PCP. In the presence of the P2-receptor antagonist suramin, the ATP induced Ca++ influx is completely inhibited, whereas Mg++ La+++, and verapamil are ineffective. It appears that the most likely (and unique) mechanism of ATP induced increase of cytosolic Ca++ in FRT cells is an increased influx through the activation of a P2 receptor operated Ca++ channel. © 1993 Academic Press, Inc.