Movement of strontium ions into mast cells and its relationship to the secretory response

Abstract

1. Non-stimulated mast cells take up (89)Sr and (45)Ca. There is a rapid phase of uptake of both labels which is complete in 1 min and the (89)Sr uptake is similar in magnitude to the (45)Ca uptake. A further slower phase of uptake occurs in the period from 1 to 30 min of incubation. The magnitude of this slower phase is about 6 times greater for (89)Sr than for (45)Ca.2. Non-stimulated and antigen-stimulated mast cells accumulate Sr which can be measured by atomic absorption spectroscopy. There is a direct relationship between Sr accumulation and histamine secretion which is independent of whether or not the cells are stimulated. 10% histamine secretion is associated with Sr accumulation of 0.25 f-mole/cell.3. The time course of (89)Sr uptake is similar to the time course of histamine secretion in non-stimulated cells.4. The uptake of (89)Sr is linearly related to the external Sr concentration in the range 0.5-16 m-mole/l. for both stimulated and non-stimulated cells.5. Ca, 10-1000 mumole/l. inhibits (89)Sr uptake in non-stimulated cells.6. Inhibition of glycolysis and oxidative phosphorylation prevents spontaneous histamine secretion in the presence of Sr without blocking the accumulation of Sr by the cells.7. Dibutyryl cyclic AMP, 10 m-mole/l. produces only 18% inhibition of (89)Sr uptake whereas histamine secretion is inhibited by 45% by the same concentration. The antigen-stimulated Sr uptake on the other hand can be completely inhibited by dibutyryl cyclic AMP, 10 m-mole/l.8. The uptakes of (89)Sr and Sr by unstimulated mast cells after 60 min incubation are dependent on extracellular H ion concentration. Both uptakes increase with increasing pH over the range pH 7-8.5.