Increased factor VII coagulant activity in the rabbit following diet-induced hypercholesterolaemia. Evidence for increased conversion of VII to alpha VIIa and higher flux within the coagulation pathway.

Factor VII coagulant activity (VIIc) is considerably higher in rabbits fed a 1% cholesterol-supplemented diet than in rabbits fed a standard diet. This increase was statistically significant 4-6 days from the beginning of treatment and rose to about 300% during the 100 days of treatment. Treatment is also associated with a 20-fold increase in plasma cholesterol concentration with the major fraction of excess cholesterol associated with the very low and intermediate density lipoprotein fractions. In both groups of rabbits, the direction and extent of variation in VIIc generally coincided with variation in cholesterol, so that over time there were significant and positive correlations between plasma cholesterol concentration in both the rabbits fed the standard diet and the rabbits fed the cholesterol-supplemented diet. The increase in VIIc was due to a higher proportion of the more active alpha VIIa in the plasma of hypercholesterolaemic rabbits rather than to an increase in the concentration of the single-chain protein. The plasma concentration of factor X and prothrombin had increased in the hypercholesterolaemic rabbits by 10 days from the beginning of treatment and both proteins were maintained at 150-200% of the concentrations in the plasma of rabbits fed the standard diet. However, these differences were only seen when the factor X and prothrombin were assayed using synthetic substrates. The specific coagulation assays for these two factors revealed no differences between the groups of animals up to 100 days.