Am J Physiol Cell Physiol Email Content Delivery
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Am J Physiol Cell Physiol 272: C1211-C1221, 1997;
0363-6143/97 $5.00
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Lara, B.
Right arrow Articles by Garcia, A. G.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Lara, B.
Right arrow Articles by Garcia, A. G.

AJP - Cell Physiology, Vol 272, Issue 4 C1211-C1221, Copyright © 1997 by American Physiological Society

ARTICLES

A caffeine-sensitive Ca2+ store modulates K+-evoked secretion in chromaffin cells

B. Lara, M. G. Lopez, M. Villarroya, L. Gandia, L. Cleeman, M. Morad and A. G. Garcia
Departamento de Farmacologia y Terapeutica, Facultad de Medicina, Universidad Autonoma de Madrid, Spain.

Catecholamine release from bovine adrenal medulla chromaffin cells superfused with a Krebs-N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid solution was monitored on-line with an electrochemical detector. Caffeine (10 mM) progressively depressed the magnitude of secretory responses to depolarizing pulses of 70 mM K+ and 2 mM Ca2+ (70 K+/2 Ca2+) in cells superfused with a Krebs-N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid solution containing 0 mM Ca2+ + 0.5 mM EGTA; blockade reached 80% at the third 70 K+/2 Ca2+ challenge given in the presence of caffeine. A similar effect was obtained when, instead of continuous superfusion, prepulses of caffeine were applied (10 mM for 60 s). The blocking effects of caffeine on K+-induced secretion depended on the time of exposure to the drug: the longer the exposure time the greater the blockade. The recovery of the K+ secretory responses previously impaired by caffeine was always gradual and followed a staircase mode. This contrasts with the effects of caffeine on various parameters measuring Ca2+ entry through Ca2+ channels, which did not parallel its effects on K+-evoked secretion. The secretion data, however, are compatible with the disappearance and recovery of an intracellular Ca2+ concentration signal triggered by K+ in single chromaffin cells loaded with fura 2 and treated with 10 mM caffeine. Thus, contrary to previous views, the depression of secretion by caffeine does not seem to be associated with inhibition of extracellular Ca2+ entry through Ca2+ channels. These functional data are, rather, compatible with the view that the degree of filling of a caffeine-sensitive intracellular Ca2+ store might regulate the extent of exocytosis. When emptied, such a store might act as a sink for the external Ca2+ entering through Ca2+ channels during cell depolarization, thus decreasing the intracellular Ca2+ concentration available for exocytosis.


This article has been cited by other articles:


Home page
 Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
F.-L. Zhao, S.-G. Lu, and S. Herness
Dual actions of caffeine on voltage-dependent currents and intracellular calcium in taste receptor cells
Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2002; 283(1): R115 - R129.
[Abstract] [Full Text] [PDF]

Home page
 J. Neurosci.Home page
D. Krizaj, J.-X. Bao, Y. Schmitz, P. Witkovsky, and D. R. Copenhagen
Caffeine-Sensitive Calcium Stores Regulate Synaptic Transmission from Retinal Rod Photoreceptors
J. Neurosci., September 1, 1999; 19(17): 7249 - 7261.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Visit Other APS Journals Online