Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we will assume that you are happy to receive all cookies and you will not see this message again. Click 'Find out more' for information on how to change your cookie settings.

1. To investigate the mechanisms regulating the reuptake of secretory granule membranes following regulated exocytosis, we have monitored changes in cell capacitance in single pancreatic beta-cells. 2. Membrane retrieval (endocytosis) occurred both in a continuous manner and in abrupt steps, corresponding to the simultaneous retrieval of 50-100 granules. The large endocytotic steps were associated with a conductance change of about 1 nS which we attribute to the formation of a fission pore with a pore radius of approximately 1 nm. 3. In some cells, we observed large amplitude capacitance fluctuations, suggesting that aggregates of granules are connected to the plasma membrane by a single pore and are subsequently retrieved as a single unit. 4. Endocytosis was evoked by elevation of cytosolic [Ca2+]i, but once initiated, a sustained increase in [Ca2+]i was not required for endocytosis to continue. 5. The [Ca2+]i dependence of exo- and endocytosis was studied by photorelease of Ca2+ from the 'caged' precursor Ca(2+)-nitrophenyl-EGTA (Ca(2+)-NP-EGTA). Both exo- and endocytosis were initiated at between 0.5 and 2 microM Cai(2+). The rate of endocytosis saturated above 2 microM Cai(2+), whereas exocytosis continued to increase up to 4 microM Cai(2+). The maximum rate of endocytosis was < 25% of that of exocytosis. 6. Unlike exocytosis, endocytosis proceeded equally well in the presence or absence of Mg-ATP. 7. Our data indicate that in the pancreatic beta-cell, exocytosis and endocytosis are regulated by different mechanisms.


Journal article


J Physiol

Publication Date



493 ( Pt 3)


755 - 767


Adenosine Triphosphate, Animals, Calcium, Cytoplasmic Granules, Cytosol, Electrophysiology, Endocytosis, In Vitro Techniques, Islets of Langerhans, Kinetics, Membrane Potentials, Mice, Microdialysis, Patch-Clamp Techniques, Spectrometry, Fluorescence