COOLING SENSITIVE [CA2-PROTEIN-COUPLED RECEPTORS(](I) RESPONSE ASSOCIATED WITH SIGNALING OF G)

The influence of cooling on the intracellular concentration of Ca2+ ([ Ca2+](i)) was tested in cell lines expressing chemical receptors, Firs t, when ATP was externally added to rat basophilic leukemia (RBL-2H3) cells, cooling from 37 degrees C to 27 degrees C induced a transient r apid increase in [Ca2+](i). In the absence of extracellular Ca2+, the [Ca2+](i) response was induced whereas an inhibitor of microsomal Ca2 ATPase, thapsigargin, largely abolished the [Ca2+](i) response, sugge sting that the internal Ca2+ stores liberate the Ca2+ ,A purinergic re ceptor antagonist, suramin, completely inhibited the [Ca2+](i) respons e to the cooling. Secondly, when serotonin (5-HT) was added to rat gli oma C6BU-1 cells, the cooling induced a transient increase in [Ca2+](i ). This [Ca2+](i) response was induced in the absence of external Ca2, suggesting that the internal Ca2+ stores liberate the Ca2+. These re sults raise the possibility that some G protein-coupled receptors are sensitive to cooling in the presence of agonist for the receptor. (C) 1998 Academic Press.