These results showed that H2O2 and NH4Cl had a similar effect in both strains of astrocytes

13C-lactate, with many labeled metabolites present after 12 h. In glucose-deprived and hypoxic conditions, after 12 h incubation with 40 mM 13C-lactate, the 13C spectra of R3230Ac cell lysates show evidence of the lactate peak but no corresponding labeled metabolites. This indicates that although hypoxic cells can take up lactate, it is cannot be utilized for metabolite generation. Catabolism of Exogenous Lactate in Breast Cancer Discussion Our study shows that breast cancer cells tolerated and catabolized lactate at concentrations found in human breast cancer. Breast cancer cell lines showed different rates of lactate uptake and generation of similar catabolites in vitro and in vivo. In vivo, uptake of lactate occurred more quickly than uptake of glucose in tumor tissue, and this uptake coincided with perfused of the tumor. In vitro, hypoxic breast cancer cells did not show catabolism of lactate. Taken together, our study strongly supports one side of the metabolic symbiont model: the assertion that aerobic breast cancer cells can tolerate and metabolize lactate. Our autoradiography data provide further evidence that the metabolic symbiont model may operate in some solid tumors. Manipulation of lactate uptake and catabolism was accomplished with use of CHC, but higher concentrations of CHC killed breast cancer cells in a manner that was not dependent upon the presence of lactate. This suggests that cytotoxic activity of CHC is unpaired from lactate metabolism in our model. In the past we have shown that lactate can be used as a substrate for aerobic cancer cells and that MCT1 and MCT4 expression correlate with the ability of certain cancer cell lines to consume lactate. Here, we showed that cellular responses to exogenous lactate varied depending upon cell type and glucose availability, but, overall, at concentrations seen in human breast cancer, lactate was well-tolerated and catabolized. Cell lines that consume more lactate showed less of a reliance on glucose for cell growth compared to cell lines that consumed less lactate . The R3230Ac tumors demonstrated a significantly higher kinetic uptake rate for lactate than for glucose and showed no changes in cell survival with glucose-deprivation, providing additional evidence for a high lactateconsuming phenotype. In all of the UPF 1069 site experiments conducted, the concentration of glutamine was not altered, and therefore 1417961 present at concentrations of the manufacturer’s supplementation. Glutamine has been shown to be an important metabolite for growth of cancer cell lines in culture; therefore, we chose to not remove it. Previous reports indicate that the contribution of glutamine to lactate formation is approximately 713%, depending on the growth phase and other metabolites in the culture media. While glutamine may contribute to a small amount of lactate formation, the major metabolite responsible for lactate formation is glucose. The significance of convergent pathways of glutamine and lactate metabolism may warrant future study, especially in tumor cells that may demonstrate less of a dependence on glucose as a primary substrate. For lactate to act as an energy substrate, it needs to be converted to pyruvate, enter the mitochondria and go through oxidative phosphorylation. Through use of labeled lactate, it has been previously found that lactate completes the course of oxidative phosphorylation, as shown by generation of 22924972 labeled CO2. Likewise, we found that R3230Ac cells significantly increased 13C-lactate, with many labeled metabolites present after 12 h. In glucose-deprived and hypoxic conditions, after 12 h incubation with 40 mM 13C-lactate, the 13C spectra of R3230Ac cell lysates show evidence of the lactate peak but no corresponding labeled metabolites. This indicates that although hypoxic cells can take up lactate, it is cannot be utilized for metabolite generation. Catabolism of Exogenous Lactate in Breast Cancer Discussion Our study shows that breast cancer cells tolerated and catabolized lactate at concentrations found in human breast cancer. Breast cancer cell lines showed different rates of lactate uptake and generation of similar catabolites in vitro and in vivo. In vivo, uptake 18083779 of lactate occurred more quickly than uptake of glucose in tumor tissue, and this uptake coincided with perfused of the tumor. In vitro, hypoxic breast cancer cells did not show catabolism of lactate. Taken together, our study strongly supports one side of the metabolic symbiont model: the assertion that aerobic breast cancer cells can tolerate and metabolize lactate. Our autoradiography data provide further evidence that the metabolic symbiont model may operate in some solid tumors. Manipulation of lactate uptake and catabolism was accomplished with use of CHC, but higher concentrations of CHC killed breast cancer cells in a manner that was not dependent upon the presence of lactate. This suggests that cytotoxic activity of CHC is unpaired from lactate metabolism in our model. In the past we have shown that lactate can be used as a substrate for aerobic cancer cells and that MCT1 and MCT4 expression correlate with the ability of certain cancer cell lines to consume lactate. Here, we showed that cellular responses to exogenous lactate varied depending upon cell type and glucose availability, but, overall, at concentrations seen in human breast cancer, lactate was well-tolerated and catabolized. Cell lines that consume more lactate showed less of a reliance on glucose for cell growth compared to cell lines that consumed less lactate . The R3230Ac tumors demonstrated a significantly higher kinetic uptake rate for lactate than for glucose and showed no changes in cell survival with glucose-deprivation, providing additional evidence for a high lactateconsuming phenotype. In all of the experiments conducted, the concentration of glutamine was not altered, and therefore present at concentrations of the manufacturer’s supplementation. Glutamine has been shown to be an important metabolite for growth of cancer cell lines in culture; therefore, we chose to not remove it. Previous reports indicate that the contribution of glutamine to lactate formation is approximately 713%, depending on the growth phase and other metabolites in the culture media. While glutamine may contribute to a small amount of lactate formation, the major metabolite responsible for lactate formation is glucose. The significance of convergent pathways of glutamine and lactate metabolism may warrant future study, especially in tumor cells that may demonstrate less of a dependence on glucose as a primary substrate. For lactate to act as an energy substrate, it needs to be converted 18753409 to pyruvate, enter the mitochondria and go through oxidative phosphorylation. Through use of labeled lactate, it has been previously found that lactate completes the course of oxidative phosphorylation, as shown by generation of labeled CO2. Likewise, we found that R3230Ac cells significantly increased