Intrinsic differences in heat and/or X-ray sensitivity of seven mammalian cell lines cultured and treated under identical conditions.

panisons with HeLa cells (22, 23, 29), pig kidney cells (17, 33), V79 cells (16, 36), and CHO cells (7, 20). Some studies also have shown that malignant cells cultured in vitro are more sensitive to heat treatment than the normal cell lines (11, 21, 26, 27). Because of the differences in cellular heat responses among different laboratories, it is difficult to ascertain whether the differential heat sensitivity in the malignant cells versus normal cells and of the different cell lines is due to an inherent cellular property or due to different culturing and medium conditions used in the various labo ratonies. The data presented by Freeman et al. (9), Gerweck (10), Hahn (12), Henle and Dethlefsen (19), Overgaard and Bichel (28), Power and Harris (30). Raaphorst and Dewey (32), and Schlag and LUcke-Huhle (36), demonstrate that such factors as nutritional state, growth phase, pH, oxygen concentration, and tonicity can affect the heat sensitivity of cultured mammalian cells. Therefore, differences in these environmental factors in cell cultures may produce different thermal responses in the various cell lines, thus making it difficult to determine differences in the inherent heat sen sitivity of the different cells. A study by Bhuyan et a!. (2) has shown that the heat responses of various cell lines cultured in the same labora tory are different. Although 2 of the cell lines, HeLa and L1210, were cultured in the same medium, the HeLa cells were cultured in Roswell Park Memorial Institute medium in monolayer while the L1210 cells were grown in suspension in Roswell Park Park Memorial Institute medium. Thus, the different media and culture conditions may be responsible for the observed differences in heat sensitivity. In another investigation by Hanisiadis et a!. (15), in which 4 cell lines were maintained in the same medium, except for the addi tion of Eagle's minimal essential medium and L-glutamine for 2 cell lines, a very similar heat response was observed for CHO, V79, RLB normal liver, and Morris rat hepatoma cells. In this study, we investigated the inherent differences in heat and/or radiosensitivity of 7 mammalian cell lines (CHO 10, V79, HeLa 53, mouse LP59, pig kidney CCL33, muntjac CCL157, and rat kangaroo CCL56) cultured in exponential growth phase in attached monolayer using F12 medium. All culture conditions were carefully controlled so that all cell lines were cultured in an identical manner, and all expeni mental procedures were identical for all the cell lines. ABSTRACT