The glycogen content of rat peritoneal mast cells (mean: 3 nmoles/10(6) cells) was increased 15% by incubation with glucose (1 mM) and reduced 35% when incubated without glucose at 37 degrees C for 15 min. The storage capacity for glycogen is thus low. Lactate production at 37 degrees C in a substrate-free medium was low (2.5-6.3 nmoles/10(6) cells in 40 min), but was stimulated 5-fold in the aerobic medium and 10-15 fold in the anaerobic medium by glucose. Both aerobic and anaerobic glycolysis in presence of glucose can thus provide energy for histamine secretion. The initial enzymes of the pentose phosphate pathway, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, have been demonstrated in mast cells. The enzyme activity in mast cells was, however, low compared to the high activity in the other peritoneal cells. The extent of the pentose cycle activity was determined from the conversion of 14C1- and 14C6-glucose to 14CO2, expressing the specific 14CO2 yields as fractions of the total glucose utilization. The normal pentose cycle activity with 1 mM glucose was 0.4% of the glucose metabolism. This was remarkably simulated by an electron acceptor, phenazine methosulfate. The pentose cycle was enhanced to 0.71% (80% stimulation) after exposure of the mast cells to compound 48/80, causing 68% histamine release. The stimulation of the pentose cycle by compound 48/80 seems to be due to the enhancement of biosynthetic processes during the regenerative phase.(ABSTRACT TRUNCATED AT 250 WORDS)