NO EVIDENCE FOR FEEDBACK INHIBITION OF HEPATIC APOLIPOPROTEIN-B (APO-B) PRODUCTION AFTER EXTRACORPOREAL LOW-DENSITY-LIPOPROTEIN PRECIPITATION AS DETERMINED BY [1-C-13]LEUCINE INFUSION IN NORMAL VOLUNTEERS

To determine the impact of an acute reduction of the circulating mass of apolipoprotein B (apo B) on apo B metabolism we studied six healthy male volunteers before (day 0), 1 day after (day 2), and 7 days after (day 8) an LDL apheresis treatment which reduced apo B mass by 59%. A ppearance of newly synthesized apo B in plasma VLDL and LDL was studie d using a primed-constant infusion of [1-C-13]-leucine. VLDL apo B poo l size and fractional VLDL apo B production rate calculated using a on e-compartment model were similar on all 3 study days. Absolute VLDL ap o B production was not statistically different throughout the study (1 9.7 +/- 12.3, 19.5 +/- 7.5, 29.1 +/- 17.7 mg kg-1 day-1). LDL apo B fr actional production rate was increased on day 2 (0.38 +/- 0.17, 0.68 /- 0.08, 0.37 +/- 0.06 pools day-1 on days 0, 2, and 8; P < 0-0 1). Ab solute LDL apo B production, however, remained constant throughout the study (10.8 +/- 3.3, 11.0 +/- 1.9, 10.8 +/- 3.1 mg kg-1 day-1). We co nclude that in healthy male volunteers acute reduction of the circulat ing apo B mass by LDL apheresis does not affect apo B metabolism signi ficantly.