In 36 normolipemic pigs randomized to a 4-week feeding with regular pig chow (n = 18, control group) or chow supplemented with cod liver oil (1 ml/kg per day) (n = 18, treated group), treatment with cod liver oil produced a significant decrease in serum cholesterol, low density lipoprotein cholesterol, and triglycerides. Deep carotid arterial wall injury (media exposed) by balloon angioplasty was associated with less 111In-labeled platelet deposition (24.6 +/- 4.8 x 10(6)/cm2 versus 62.5 +/- 17.0 x 10(6)/cm2, p less than 0.05; difference, -33.8 x 10(6)/cm2; 95% confidence interval [CI], -1.9 x 10(6)/cm2 to -73.9 x 10(6)/cm2) and injury-related vasoconstriction (21.3 +/- 2.2% versus 30.9 +/- 2.9%, p less than 0.05; difference, -9.6%; 95% CI, -2.2% to -17.0%) in the cod liver oil-treated group than in the control group; with mild injury (media not exposed), platelet deposition was low and unchanged (6.2 +/- 0.5 x 10(6)/cm2 versus 7.8 +/- 0.7 x 10(6)/cm2; difference, -1.6 x 10(6)/cm2; 95% CI, -1.1 x 10(6)/cm2 to +4.3 x 10(6)/cm2), but associated vasoconstriction was reduced respectively (16.3 +/- 2.0% versus 23.0 +/- 2.2%, p less than 0.05; difference, -6.7%; 95% CI, -0.6% to -12.8%). When arterial blood from cod liver oil-treated pigs superfused normal aortic media ex vivo, platelet deposition onto the normal aortic media was lower than when arterial blood from control pigs superfused the normal aortic media (43.7 +/- 8.8 x 10(6)/cm2 versus 66.8 +/- 13.0 x 10(6)/cm2, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)