AJP - Heart and Circulatory Physiology, Vol 247, Issue 3 440-H445, Copyright © 1984 by American Physiological Society
Effects of metabolized and unmetabolized arachidonate on rat platelet shape change
M. G. Lampugnani and G. de Gaetano
Arachidonate (0.12-1.5 mM) initiated a concentration-dependent, saturable
shape change of rat platelets suspended in citrated plasma. Interaction of
arachidonate with platelets led to the formation of active metabolites that
appeared to be the actual inducers of shape change. Among these,
prostaglandin endoperoxides rather than thromboxane A2 seemed necessary for
shape change. No role of the products of the lipoxygenase pathway could be
shown. In the presence of cyclooxygenase and lipoxygenase inhibitors,
arachidonate (0.25-0.5 mM) prevented platelet shape change induced by the
endoperoxide analog U-46619 but not by other agonists such as ADP or
serotonin. Arachidonate acts therefore as both an agonist and an antagonist
of platelet shape change. The agonistic effect requires arachidonate
metabolism while the antagonistic activity seems to be linked to the fatty
acid molecule itself.
