About 95% of venom of the imported fire ant Solenopsis invicta is comp
osed of dialkyl piperidines. These alkaloids produce a distinct pustul
e at the site of injection. The formation of this pustule may involve
the activation of platelets and neutrophils. The purpose of this paper
was to characterize the effects of fire ant venom alkaloids (FAVA) on
certain physiological and biochemical functions of human platelets an
d neutrophils. In platelets, FAVA caused a rise in intracellular [Ca2], secretion of dense granules as measured by ATP release, and aggrega
tion as measured by light transmission through a suspension of platele
ts. Aggregation response was less complete with FAVA than with thrombi
n or PAF. However, secretion response was greater with FAVA than throm
bin. One of our most significant findings was that pretreatment of pla
telets with subthreshold concentrations of FAVA produced enhanced PAF-
induced increase in [Ca2+]cyt, suggesting that synergism between the t
wo agonists might play an important role in the physiological response
to FAVA. In neutrophils, FAVA produced a rise in intracellular [Ca2+]
and aggregation, although the responses were more moderate than those
observed in platelets. These results suggest that FAVA activation of
platelets and neutrophils may occur in vivo as a response to stings by
red fire ants.