Studies on Platelet Factor 4 Like Activity in Atherosclerosis Susceptible and Resistant Pigeons

Recent studies suggest that a platelet factor(s) may be implicated in the stimulation of the smooth muscle cell proliferation occurring at the initial stages of atherosclerosis. Platelet factor 4 like activity in serum (PF4 = units of heparin neutralized by serum heated to 60° C) was measured at sequential ages in 9 White Carneau pigeons which develop spontaneous atherosclerosis first grossly apparent a 1 year of age (susceptible pigeons) and in 9 Show Racer pigeons which do not develop atherosclerosis (resistant pigeons). The susceptible pigeons developed progressive elevation of serum PF4, the maximal rate of increase being between 6 months (2.05u.) and 1 year (4.05 u.) (p < 0.001) and persisting at 3 years (3.40 u.). By contrast, in the resistant pigeons serum PF4 fell progressively from age 6 months (2.05 u.) to 1 year (1.85 u.) and 3 years (1.45 u.) (p < 0.001). Preliminary studies on thrombocyte count, size and ultrastructure transmission and scanning electronmicroscopy show no obvious differences between the two species of pigeons except for a more irregular and less pseudopodic surface in the thrombocyte of the susceptible pigeons.

The study suggests that platelet factor 4 may be correlated with the initiation of atherosclerosis in the pigeon.