| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Biophys J, January 2002, p. 226-232, Vol. 82, No. 1
and
*Laboratory of Neuroendocrinology-Molecular Cell Physiology,
Institute of Pathophysiology, Medical School, and
Department of Physics, Faculty of Mathematics and
Physics, 1001 Ljubljana, Slovenia; Molecular
Biophysics Unit, Indian Institute of Science, Bangalore 560012, India; and §Celica, Biomedical Sciences Center,
1000 Ljubljana, Slovenia
We have used the patch-clamp technique to monitor changes
in membrane capacitance (Cm) elicited by
fast and spatially homogeneous rises in cytosolic calcium concentration
([Ca2+]i) using flash photolysis of NP-EGTA.
Average peak [Ca2+]i amplitudes of 20-25
µM triggered three different types of responses in
Cm: (i) In 42% of cells, a rise in
[Ca2+]i activated a monotonic increase in
Cm followed by a slow decline to resting
values; (ii) In 30% of cells, the rise in
Cm was clearly characterized by two dynamic
components, consisting of a rapid and a slow exo-endocytosis cycle;
(iii) In 28% of cells, after the initial rapid rise in
Cm, endocytosis exhibited excess retrieval that was characterized by a decline in Cm
below resting Cm. The aim of this work is to
develop a unified mathematical model with a minimum number of
parameters that would describe all the observed types of responses.
Three models were considered: Model A, a model with a single component
of exo-endocytosis cycle; model B, a model consisting of a sum of two
independent dynamic components; and model C, a model in which, in
addition to the two dynamic components as in model B, excess retrieval
due to a lipid flow through the reversal closing of the fusion pore
during the rapid component of exo-endocytosis cycle was considered. The
results show that the latter model describes all the types of responses
in Cm recorded in rat melanotrophs. The
association of excess retrieval exclusively with the rapid, but not the
slow, exocytosis indicates that some fusing vesicles mediate a lipidic
flux during the reversal closing of the fusion pore, whereas those
entering the slow phase of exocytosis may fuse with the plasma membrane
completely and are retrieved by other endocytic machinery, independent
of the lipid flow that might have occurred as the fusion pore opened permanently.
Biophys J, January 2002, p. 226-232, Vol. 82, No. 1
© 2002 by the Biophysical Society 0006-3495/02/01/226/07 $2.00
This article has been cited by other articles:
 |
|
 |
|
  J. H. Kim, J. H. Nam, M.-H. Kim, D.-S. Koh, S.-J. Choi, S. J. Kim, J. E. Lee, K. M. Min, D.-Y. Uhm, and S. J. Kim Purinergic Receptors Coupled to Intracellular Ca2+ Signals and Exocytosis in Rat Prostate Neuroendocrine Cells J. Biol. Chem., June 25, 2004; 279(26): 27345 - 27356. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Kreft, D. Krizaj, S. Grilc, and R. Zorec Properties of Exocytotic Response in Vertebrate Photoreceptors J Neurophysiol, July 1, 2003; 90(1): 218 - 225. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Kreft, V. Kuster, S. Grilc, M. Rupnik, I. Milisav, and R. Zorec Synaptotagmin I increases the probability of vesicle fusion at low [Ca2+] in pituitary cells Am J Physiol Cell Physiol, February 1, 2003; 284(2): C547 - C554. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
