Changes of intracellular calcium concentration ([Ca2(+)](i)) induced b
y the extracellular application of ATP and bradykinin in mouse mammary
tumour cells (MMT060562) were investigated by image analysis of fluo-
3 fluorescence at 24 degrees C and 35 degrees C. ATP (0.1-100 mu M) an
d bradykinin (0.1 nM-1 mu M) induced the increase of[Ca2+](i) at both
temperatures and Ca2+-depletion did not affect these [Ca2+](i) respons
es. Both [Ca2+](i) responses became more sensitive at 35 degrees C tha
n at 24 degrees C. A clear latency of [Ca2+](i) increase after the app
lication of the agonists was observed, and it changed with the concent
ration of the agonist. As concentrations of ATP or bradykinin became l
ower, the latency and rise time became longer. At higher concentration
s, the latency and rise time approached a constant value. The latency
shortened remarkably at 35 degrees C. These results suggested the invo
lvement of a regenerative or threshold process in the [Ca2+](i) respon
ses in mammary tumour cells. (C) 1997 by John Wiley & Sons, Ltd.