Calcium dependence of action potential-induced endocytosis in chromaffin cells.

摘要: Exocytosis occurs via fusion of transmitter-containing granules with the cell membrane, whereupon granule contents are released and membrane surface area increases. is followed by endocytosis to maintain proper composition. We have shown that adrenal chromaffin cells internalize in a biphasic manner following action potential stimulation. At basal firing rates (single - 0.5 Hz trains) rapid retrieval (termed Phase I) independent activity protein phosphatase calcineurin wanes efficiency activity. intermediate frequencies (>6 Hz) second, calcineurin-sensitive, form activity-enhanced emerges (Phase II). In this study, we employ electrophysiological, electrochemical, computational techniques estimate intracellular Ca(2+) at site measuring secretion rates. The measured yield estimates [Ca(2+)](i) based on kinetic scheme for exocytosis calibrated under highly controlled [Ca(2+)](i). Based analysis, propose I inhibited cytosolic K(inh)=605 nM, while II activated K(act)=1.46 micro M. Molecular processes may be consistent behaviors discussed.