The involvement of the Na(+)/H(+) exchanger in the formation of microvesicles by porcine platelets.
Activated platelets release microvesicles, which express procoagulant activity. The mechanism by which vesicles are formed is not entirely clear. This study was undertaken to determine whether a link exists between the operation of the plasma membrane Na(+)/H(+) exchanger (NHE) and vesiculation. It was found, that platelets treated with NHE-simulating monensin and the sodium influx-inducing gramicidin (without concomitant H+ efflux) produced vesicles demonstrating procoagulant activity. Alkalinization of platelet cytosol by NH4Cl failed to evoke vesicle release. Collagen and phorbol ester (PMA)-evoked vesiculation was diminished in the presence of 5-(N-ethyl-N-isopropyl amiloride) (EIPA, inhibitor of NHE) or GF 109203X (inhibitor of protein kinase C). Vesicle formation induced by collagen, PMA, and the calcium ionophore A23187 was less pronounced in the absence of external Na+. In comparison with collagen, thrombin was a stronger inducer of vesiculation. Platelets stimulated by thrombin, collagen, and PMA accumulated 22Na+, a phenomenon inhibited in the presence of EIPA. Collagen-evoked vesicle formation started with aggregation but culminated after its completion. The data indicate a significant contribution of the Na(+)/H(+) exchanger in the formation of microvesicles by porcine platelets.
Stelmach
Halina
H
Department of Physical Chemistry, Medical Academy of Bialystok, Mickiewicza 2A, 15-230 Bialystok, Poland.
Rusak
Tomasz
T
Tomasiak
Marian
M
D000818:Animals; D001777:Blood Coagulation; D001792:Blood Platelets / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure*; D003094:Collagen / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D007476:Ionophores / Q000494:pharmacology; D008563:Membrane Lipids / Q000032:analysis; D010703:Phorbol Esters / Q000494:pharmacology; D015539:Platelet Activation; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000502:physiology*; D013552:Swine; D013917:Thrombin / Q000494:pharmacology
D007476:Ionophores; D008563:Membrane Lipids; D010703:Phorbol Esters; D017923:Sodium-Hydrogen Exchangers; D003094:Collagen; D012964:Sodium; D013917:Thrombin