We report here the technique for detection and measurement of the temperature changes in single cells using a recently devised microthermometer (a glass micropipette filled with the thermosensitive fluorescent dye Europium (III) thenoyltrifluoroacetonate trihydrate). We found that the heat production in a single HeLa cell occurred with some time delay after the ionomycin-induced Ca2+ influx from the extracellular space. The time delay inversely depended on extracellular [Ca2+], and the increase in temperature was suppressed when Ca2+-ATPases were blocked by thapsigargin. These observations strongly suggest that the enzymatic activity of Ca 2+-ATPases in endoplasmic reticulum leads to the heat production. This study has therefore paved the way for studying the thermogenesis at the single-cell level.
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