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Characterization of Prostaglandin E 2 ‐Induced Ca 2+ Mobilization in Single Bovine Adrenal Chromaffin Cells by Digital Image Microscopy
Author(s) -
Ito Seiji,
MochizukiOda Noriko,
Hori Kunio,
Ozaki Kazuho,
Miyakawa Atsuo,
Negishi Manabu
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb08182.x
Subject(s) - histamine , medicine , endocrinology , egta , prostaglandin e , prostaglandin e2 , pertussis toxin , chemistry , calcium , biology , g protein , receptor
We recently reported that prostaglandin E 2 (PGE 2 ) stimulates phosphoinositide metabolism accompanied by an increase in intracellular free Ca 2+ concentration ([Ca 2+ ] i ) in cultured bovine adrenal chromaffin cells. In the present study, temporal and spatial changes in [Ca 2+ ] i induced by PGE 2 in fura‐2‐loaded individual cells were investigated by digital image microscopy and were compared with those induced by nicotine and histamine. Image analysis of single cells revealed that responses to PGE 2 showed asynchrony with the onset of [Ca 2+ ] i changes. After a lag time of 10–30 s, PGE 2 ‐induced [Ca 2+ ] i changes took a similar prolonged time course in almost all cells: a rapid rise followed by a slower decline to the basal level over 5 min. Few cells exhibited oscillations in [Ca 2+ ] i . In contrast, nicotine and histamine induced rapid and transient [Ca 2+ ] i changes, and these [Ca 2+ ] i changes were characteristic of each stimulant. Whereas pretreatment of the cells with pertussis toxin (100 ng/ml, 6 h) did not block the response to any of these stimulants, treatment with 12‐ O ‐tetra‐decanoylphorbol 13‐acetate (100 n M , 10 min) completely abolished [Ca 2+ ] i changes elicited by PGE 2 and histamine. In a Ca 2+ ‐free medium containing 3 m M EGTA, or in medium to which La 3+ was added, the [Ca 2+ ] i response to nicotine disappeared, but that to histamine was not affected significantly. Under the same conditions, the percentage of the cells that responded to PGE 2 was reduced to 37% and the prolonged [Ca 2+ ] i changes induced by PGE 2 became transient in responding cells, suggesting that the maintained [Ca 2+ ] i increase seen in normal medium is the result of a PGE 2 ‐stimulated entry of extracellular Ca 2+ . Whereas the organic Ca 2+ ‐channel blocker nicardipine inhibited [Ca 2+ ] i changes by all stimulants at 10 μ M , these [Ca 2+ ] i changes were not affected by any of the organic Ca 2+ ‐channel blockers, i.e., verapamil, diltiazem, nifedipine, and nicardipine, at 1 μ M , a concentration high enough to inhibit voltage‐sensitive Ca 2+ channels. These results demonstrate that PGE 2 may promote Ca 2+ entry with concomitant release of Ca 2+ from intracellular stores and that the mechanism(s) triggered by PGE 2 is apparently different from that by histamine or nicotine.