1. Seven patients with type II hyperlipoproteinaemia were treated with the bile acid-sequestering resin, colestipol (5 g three times daily), after a prolonged period of taking placebo.
2. After 8–9 weeks of treatment, the plasma concentration of the non-esterified cholesterol of very-low-density lipoprotein (VLDL) had risen by a mean of 0.09 mmol/l (43% increase, P < 0.001), that of the esterified cholesterol of VLDL had risen by a mean of 0.11 mmol/l (38% increase, P < 0.01), and that of the triglyceride of VLDL had risen by a mean of 0.40 mmol/l (53% increase, P<0.001). During the same period, the plasma concentration of the non-esterified cholesterol of low-density lipoprotein (LDL) decreased by a mean of 0.44 mmol/l (26% decrease, P < 0.01), that of the esterified cholesterol of LDL decreased by a mean of 1.28 mmol/l (30% decrease, P< 0.001), and that of the triglyceride of LDL decreased by a mean of 0.04 mmol/l (8% decrease, P < 0.01). No significant changes occurred in the plasma concentration of either the cholesterol or triglyceride of high-density lipoprotein (HDL) during treatment.
3. During the early period of treatment with colestipol, changes took place in the specific radioactivity of plasma cholesterol (labelled by intravenous injection of [3H]cholesterol), which, together with the changes in the mass of cholesterol within the individual plasma lipoproteins, were consistent with an increased influx into plasma of non-esterified cholesterol within VLDL, and an increased efflux of cholesterol from plasma within LDL.