Summary
Frog thrombocytes were shown to aggregate in response to thrombin, collagen, and adenosine
triphosphate (ATP). Microscopic observations indicated that collagen and thrombin
induced aggregates were cell-to-cell in nature and not due solely to passive adherence
to collagen or fibrin strands.
The ability of ATP to promote aggregation suggested that the release of this nucleotide
might be the mechanism by which frog thrombocytes aggregate ; however, there was no
evidence to support this hypothesis. Enzymatic hydrolysis of ATP by hexokinase had
no effect on thrombin-induced aggregation, and ATP could not be identified in the
supernatants of aggregated thrombocytes. Nevertheless, the ability of these cells
to aggregate in response to these aggregating agents indicates that significant parallels
may exist between platelet aggregation and the aggregation of non-mammalian thrombocytes.