| Popis: |
Both brain and melanoma slices displayed similar QO2CO2 values, but marked differences occurred in QN2CO2 under certain conditions. Thus, the two tissues responded differently to added magnesium, phenol, and insulin. The first two substances markedly increased the QN2CO2 of brain but slightly inhibited that of melanoma. The QN2CO2 of brain slides was not increased by insulin but that of melanoma was (ca. 40%). As little as 0.003 mg (0.1 units) of crystalline zinc-insulin per ml was sufficient to give maximal stimulation. Crystalline zinc-insulin freed of hyperglycemic factor was as effective as regular crystalline zinc-insulin in increasing the QN2CO2 of melanoma slices. Hyperglycemic factor largely freed of insulin had no appreciable effect on QN2CO2. Zinc appears to play a critical role in connection with the influence of insulin on QN2CO2 of melanoma slices. The relative concentrations of the two substances are critical. Under aerobic conditions insulin variably increased the R.Q., QO2CO2, and absolute Pasteur effect of melanoma. QO2 (respiration) was never increased, but was sometimes decreased. Exposure of melanoma-bearing mice to 35° or 40° C, for 13 hours or more, was associated with a marked diminution in the QN2CO2 of the tumor slices as compared to tumor slices from mice exposed to ca. 20° C. Insulin increased (average 49%) the QN2CO2 of slices from the heat-treated tumors to a level approximately equal to that of slices from 20° C tumors where insulin gave only slight stimulation (average 7%); additional (12 to 44 days) exposure to 35° or 40° C resulted in marked suppression of tumor growth and further decline in the QN2CO2. |
