Increases in cytosolic Ca2+ accompany basophil activation by eosinophil granule major basic protein.
The response of basophil cytosolic free Ca2+ concentrations ([Ca2+]i) to stimulation by eosinophil granule major basic protein (MBP) was assessed using digital video microscopy. MBP stimulated an elevation in basophil [Ca2+]i that, in general, developed slowly and increased monotonically. In some experiments, however, the average rise in [Ca2+]i was biphasic, with an initial transient increase followed by a larger and more sustained elevation. At the single cell level MBP stimulation caused frequent, asynchronous oscillations in [Ca2+]i that ranged up to 300 nM in amplitude. Chelation of extracellular Ca2+ selectively blocked the second, sustained rise in [Ca2+]i as well as MBP-induced histamine release. Within individual experiments, the increase in [Ca2+]i paralleled the level of histamine release. These results demonstrate that, unlike the activation of neutrophils or eosinophils, basophil activation by MBP correlates with an elevation in [Ca2+]i. Further, the MBP induced [Ca2+]i response exhibits several features in common with the IgE-mediated [Ca2+]i response.
MacGlashan
D W
DW
Asthma and Allergy Center, Johns Hopkins University, Baltimore MD 21224, USA.
Gleich
G J
GJ
Thomas
L L
LL
D001491:Basophils / Q000187:drug effects / Q000276:immunology*; D001798:Blood Proteins / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D047091:Eosinophil Granule Proteins; D006636:Histamine Release; D006801:Humans; D017681:Hypereosinophilic Syndrome; D007091:Image Processing, Computer-Assisted; D018715:Microscopy, Video; D012260:Ribonucleases
D001798:Blood Proteins; D047091:Eosinophil Granule Proteins; D012260:Ribonucleases; D002118:Calcium