Comparison of 3H-misonidazole binding between CHO and 9L cells using the sandwich system.

3H-misonidazole binding of 9L cells was compared with that of CHO cells using an in vitro tumor analog, the sandwich system. In sandwiches there is a gradient of microenvironments, with cells adjacent to the necrotic center subjected to low concentrations of oxygen and glucose and to high concentrations of metabolites. Mixed sandwiches, having 9L and CHO cells interspersed, were used along with sandwiches of each individual cell line. MISO binding was assessed in situ, using autoradiography. Grains per cell were counted and detailed statistics were obtained on the variation in MISO binding among cells located in the same microenvironment. In all cases binding in the regions near the necrotic center was more than 50 times the binding found at the sandwich edge and found in control monolayers, indicating radiobiological hypoxia near the necrotic center. 9L cells began to significantly increase binding of MISO metabolites at a somewhat higher oxygen concentration than did CHO cells. At all oxygen tensions, average per cell binding of the 9L cells was 3 times or more that of the CHO cells, a factor greater than can be explained by the ratio of cell volumes alone. Statistical analyses of the variation in binding among cells in a given microenvironment give some evidence that in the mixed CHO/9L sandwiches there are interactions between the cells of the two different lines which affect the growth patterns of the cells. No preferred binding of misonidazole in the nucleus or cytoplasm was noted within the cells.