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Model for the regulation of platelet volume and responsiveness by the trans‐membrane Na + /K + ‐pump
Author(s) -
Marx Gerard,
Blankenfeld Avigdor,
Panet Rivka,
Gorodetsky Raphael
Publication year - 1992
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041510205
Subject(s) - ouabain , platelet , chemistry , receptor , incubation , fibrinogen , cell surface receptor , endocrinology , medicine , blood cell , biophysics , biochemistry , sodium , biology , organic chemistry
The correspondence between K + uptake in platelets to their responsiveness was studied using 86 Rb + as an analogue of K + . An average 86 Rb + uptake rate of 0.73 (± 0.140) × 10 −15 mole Rb + /min‐plt (n = 20) was observed. By the use of K + ‐influx inhibitors, we were able to distinguish three distinct 86 Rb + uptake pathways: an ouabain‐sensitive (61% ± 2% inhibitable) pump and two equivalent channels, only one of which is sensitive to furosemide. Other platelet parameters were also examined in conjunction with K + ‐uptake. Platelets incubated with ouabain exhibited an overall rise in their cell volume (MPV) with incubation time (ΔMPV = 7.4 × 10 −17 L/min 1 plt −1 ). Concomitantly, over 24 hours, a steady decrease in platelet number was recorded by blood cell coulter, which correlated inversely with the counts of particles, which by their size resemble white blood cells (r = 0.89). On a cellular level. incubation with ouabain induced greater expression of surface fibrinogen‐receptor (GPIIb), increased binding of FITC‐labelled fibrinogen, and increased responsiveness to ADP. Our observations suggest the following sequence of events: Ouabain turns off the Na + /K + ‐ATPase pump, which leads to water accumulation in platelets and concomitant increased MPV. Greater expression of fibrinogen receptors on the distended platelet surface corresponds to spontaneous microaggregate formation as well as greater respon‐siveness to agonists. Our model links volume regulation, the expression of fibrinogen receptors, and the sensitivity of platelets to agonists to the activity of the Na + K + ‐ATPase pump. © 1992 Wiley‐Liss, Inc.