Heat sensitivity, thermotolerance, and profile of protein synthesis of human bone marrow progenitors.

Hyperthermic sensitivity, kinetics of thermotolerance induction and decay, and profile of heat shock protein synthesis were studied in human granulocyte-macrophage progenitors and nucleated bone marrow cells, respectively. The D0 of the heat survival curves of human granulocyte-macrophage colony-forming cells at 43 degrees C, 44 degrees C, and 45 degrees C were 23, 12, and 5 min, respectively. The kinetics of thermotolerance induction was measured with a triggering dose of 44 degrees C/20 min, 45 degrees C/10 min, 41 degrees C/2 h, and 42 degrees C/1 h and 4 h. The cells were then challenged with 44 degrees C or 45 degrees C after incubation for 2, 4, 6, 24, and 48 h at 37 degrees C. In all cases, except for 41 degrees C/2 h, thermotolerance was maximum at 2 to 6 h, began to decay at 24 h, and decayed completely by 48 h. At the 41 degrees C/2-h triggering dose, the thermotolerance decayed completely by 24 h. The heat shock protein synthesis was measured after a triggering dose of 44 degrees C/20 min or 45 degrees C/10 min. Synthesis of Mr 70,000 and 87,000 heat shock proteins in the total nucleated bone marrow cells was evident at least for 8 h after the initial heating.