Association of 45calcium with rat mast cells stimulated by 48/80: effects of inactivation, calcium and metabolic inhibition.

Abstract

1. Stimulation by compound 48/80 of mast cells deprived of Ca released histamine when Ca was subsequently added. This secretory response was accompanied by a pronounced increase in the amount of cell-associated (45)Ca.2. The level of cell-associated (45)Ca declined as the interval between stimulation by compound 48/80 and the introduction of (45)Ca increased.3. This decline in the amount of (45)Ca paralleled the decline in histamine secretion that is called inactivation and each curve could be fitted by linear regression to a first-order equation with a half-life of between 1 and 2 min.4. When histamine secretion was held constant, the amount of cell-associated (45)Ca steadily and significantly declined as the interval between stimulation and the addition of (45)Ca increased. This decline in the level of (45)Ca was significantly reduced when fully inactivated cells were used.5. The amount of cell-associated (45)Ca could not be significantly reduced by repeated or prolonged washing with EGTA or LaCl(3).6. The addition of the ionphore, A23187, or compound 48/80, to mast cells loaded with (45)Ca by prior stimulation with 48/80 and bathed in Ca-free media, significantly reduced the level of cell-associated (45)Ca. This effect of 48/80 but not of A23187 was prevented by including either dinitrophenol or (45)Ca in the extracellular solution.7. When [(3)H]N-methyl-methoxy-inulin was included with the (45)Ca or added alone, no significant change in the level of cell-associated [(3)H]inulin was found during the course of inactivation.8. Increasing the Ca concentration increased the amount of cell-associated (45)Ca when Ca was added 10 sec after stimulation by 48/80 but not when Ca was added 10 min after stimulation.9. Incubation of mast cells in media containing deoxyglucose and either antimycin A or dinitrophenol prevented both histamine release and any increase in the level of cell-associated (45)Ca in response to stimulation by 48/80. A similar result was obtained using sensitized mast cells stimulated by antigen. The addition of the ionophore, A23187, to the mast cells prompted a significant increase in the level of cell-associated (45)Ca.10. These results are considered to be support for the hypothesis that the process of inactivation to compound 48/80 results from a time-dependent decay in membrane permeability. It is suggested that those events associated with initiating changes in membrane permeability are effected by metabolic inhibition and calcium.