Abstract:
:We measured the exocytotic response induced by flash photolysis of caged compounds in isolated mast cells and chromaffin cells. Vesicle fusion was measured by monitoring the cell membrane capacitance. The release of vesicular contents was followed by amperometry. In response to a GTP gamma S stimulus we found that the time integral of the amperometric current could be superimposed on the capacitance trace. This shows that the integrated amperometric signal provides an alternative method of measuring the extent and kinetics of the secretory response. Very different results were obtained when photolysis of caged Ca2+ (DM-nitrophen) was used to stimulate secretion. In mast cells, there was an immediate, graded increase in membrane capacitance that was followed by step increases (indicative of granule fusion). During the initial phase of the capacitance increases, no release of oxidizable secretory products was detected. In chromaffin cells we also observed a considerable delay between increases in capacitance, triggered by uncaging Ca2+, and the release of oxidizable secretory products. Here we demonstrate that there can be large increases in the membrane capacitance of a secretory cell, triggered by flash photolysis of DM-nitrophen, which indicate events that are not due to the fusion of granules containing oxidizable substances. These results show that increases in capacitance that are not resolved as steps cannot be readily interpreted as secretory events unless they are confirmed independently.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Oberhauser AF,Robinson IM,Fernandez JMdoi
10.1016/S0006-3495(96)79315-3subject
Has Abstractpub_date
1996-08-01 00:00:00pages
1131-9issue
2eissn
0006-3495issn
1542-0086pii
S0006-3495(96)79315-3journal_volume
71pub_type
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