Prinmte4 in U.S.A. CERTAIN DEHYDROGENASE ACTIVITIES AND DRY WEIGHT OF NORMAL AND MALIGNANT MAST CELLS1

Total dry weight of individual lyophilized peritoneal malignant mouse mast cells (line P.815, Dunn-Potter) was found to have a mean value of 219 ± 7 pg compared with 2.4 times this for normal rat peritoneal mast cells. Lactic, glucose 6-phosphate, 6-phosphogluconate and isocitric dehydrogenase activities in suspensions of whole and of disrupted malignant cells were measured fluorometrically. The lactic dehydrogenase activity per unit weight of protein of the malignant cells was found to be about 19 times that of the normal cells, and the other enzymes, which do not appear to be present in the normal cells, were demon-strated in the malignant cells. Freeze-thawing, temperature and time of storage and pres-ence of protein influenced the individual enzyme activities differently. Protein was gener-ally protective against inactivation, and that due to freeze-thawing, which was used to disrupt cells for enzyme liberation, was minimized in the presence of serum or plasma albumin. Protein did not, however, protect against enzyme inactivation because of pro-longed storage of the cells in the frozen state. Evidence has accumulated for involvement of an energy-requiring step in the reactions leading to histamine release from mast cells (1, 2, 7, 17, 20-22, 25, 26). Since glucose has been shown to counteract the inhibitory action of anoxia and of various metabolic inhibitors on the histamine release, it has been suggested that high energy compounds generated through glycolysis could supply the needs of the energy-requiring step (e.g., Diamant, 1962 (4)). Glick and Pothapragada in 1961 (10) studied the succinic dehydrogenase system in rat pen-toneal mast cells, which, calculated from their data, had an activity of 0.24 mole/kg protein/hr. The presence of fumarase in the nongranule fraction of malignant mouse mast cells was demonstrated by histochemical staining by Hagen, Barrnett and Lee (15). The need for more information on enzymes of energy me-tabolism in mast cells prompted an investigatio