Final published version
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - Do caged-Ca2+ compounds mimic the physiological stimulus for secretion?
AU - Oberhauser, A. F.
AU - Robinson, I. M.
AU - Fernandez, J. M.
PY - 1995/12/31
Y1 - 1995/12/31
N2 - We measured the exocytotic response induced by a rapid and global increase in the concentration of Ca2+ or GTPγS (achieved by flash photolysis of caged compounds) in mast cells and chromaffin cells. Secretion was measured by following both cell membrane capacitance and amperometry. When Ca2+ was used to trigger secretion, we observed an immediate increase in capacitance, however, the first amperometric spike observed was delayed with respect to the change in capacitance (∼5 s in mast cells and ∼0.6 s in chromaffin cells). In contrast, when GTPγS was used to trigger secretion no such discrepancy was seen, both measurements reported a secretory response that was similarly delayed with respect to the stimulus. These data suggest that the capacitance increase, when triggered by a large Ca2+ step, reports events that do not result in the fusion of vesicles containing oxidizable substances. These results contrast with the smaller secretory responses evoked by the transient opening of Ca2+ channels. Under these more physiological conditions, pulsed-laser imaging studies revealed that the Ca2+ influx was localized to discrete areas at the plasma membrane. Thus the Ca2+ stimulus triggered by DM-nitrophen fails to reproduce the small localized changes seen during a physiological stimulation and creates an artifactual non-secretory capacitive response.
AB - We measured the exocytotic response induced by a rapid and global increase in the concentration of Ca2+ or GTPγS (achieved by flash photolysis of caged compounds) in mast cells and chromaffin cells. Secretion was measured by following both cell membrane capacitance and amperometry. When Ca2+ was used to trigger secretion, we observed an immediate increase in capacitance, however, the first amperometric spike observed was delayed with respect to the change in capacitance (∼5 s in mast cells and ∼0.6 s in chromaffin cells). In contrast, when GTPγS was used to trigger secretion no such discrepancy was seen, both measurements reported a secretory response that was similarly delayed with respect to the stimulus. These data suggest that the capacitance increase, when triggered by a large Ca2+ step, reports events that do not result in the fusion of vesicles containing oxidizable substances. These results contrast with the smaller secretory responses evoked by the transient opening of Ca2+ channels. Under these more physiological conditions, pulsed-laser imaging studies revealed that the Ca2+ influx was localized to discrete areas at the plasma membrane. Thus the Ca2+ stimulus triggered by DM-nitrophen fails to reproduce the small localized changes seen during a physiological stimulation and creates an artifactual non-secretory capacitive response.
KW - caged calcium
KW - capacitance
KW - fusion pore
KW - patch-clamp
KW - secretion
U2 - 10.1016/0928-4257(96)80553-5
DO - 10.1016/0928-4257(96)80553-5
M3 - Journal article
C2 - 8520573
AN - SCOPUS:0028990493
VL - 89
SP - 71
EP - 75
JO - Journal of Physiology - Paris
JF - Journal of Physiology - Paris
SN - 0928-4257
IS - 2
ER -