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Elevation of pH i is not an essential step in calcium mobilisation in fura‐2‐loaded human platelets
Author(s) -
Simpson A.W.M.,
Rink T.J.
Publication year - 1987
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(87)80208-9
Subject(s) - calcium , platelet , fura 2 , chemistry , biophysics , elevation (ballistics) , biochemistry , medicine , biology , mathematics , organic chemistry , geometry , cytosol , enzyme
Human platelets were co‐loaded with the fluorescent indicators BCECF and fura‐2 to mesure pH i and [Ca 2+ ] i and incubated with aspirin to block cyclooxygenase. Either pH i and shape change and aggregation or pH i and [Ca 2+ ] i were measured simultaneously in the same stirred cuvette, at 37°C. In Hepes‐buffered saline containing 1 mM Ca 2+ , mean resting pH i was 6.98±0.01 (SE, n = 59). Changes of pH i up to ±0.35 units, imposed by additions of NH 4 Cl, CO 2 or nigericin, produced no shape change or aggregation and only insignificant changes in [Ca 2+ ] i . Sufficient thrombin to raise [Ca 2+ ] i over 1 μM and cause rapid shape change and aggregation increased pH i by no more than 0.05 units, and the increase in pH i lagged behind the elevation of [Ca 2+ ] i . We conclude that changes in pH i do not form a necessary or sufficient component of the pathways leading to receptor‐mediated Ca 2+ mobilisation or the stimulation of shape change or aggregation.