Cancer research
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We examined the effect of rate of temperature rise on the thermosensitivity of a murine lymphoblastic leukemia. L1210 cells suspended in RPMI 1630 medium:5% fetal bovine serum at pH 7.4 were heated from 37 degrees C-42 degrees C, or 44 degrees C over variable times (immediately, 30, 60, 120, 180 min) in a circulating water bath controlled by an electronic temperature programmer. Survival of the cells using a soft agar clonogenic assay was plotted against the time at final temperature so that a Do (min of heat required to reduce survival by 63% on the exponential portion of the survival curve) could be calculated as an estimate of thermosensitivity. ⋯ We conclude that the thermosensitivity of this neoplastic cell can be altered considerably by the rate of heating. This alteration is not due to a change in membrane lipids. Furthermore, the heat shock protein at Mr 70,000 which was synthesized after immediate heating could not be demonstrated in the gradually heated L1210 leukemia cells.