(A) Mice were injected with tyloxapol to block peripheral TG uptake, and plasma concentrations were measured at the indicated time points. Values indicate the mean ± SEM (n = 6–9 mice per group). (B) TG secretion rates calculated from the changes in plasma concentrations between 30 and 120 minutes in A. *P < 0.05, by Student’s t test. (C) Autoradiogram of SDS-polyacrylamide gel showing ³⁵S-labeled plasma proteins collected 120 minutes after injection with ³⁵S-methionine. Each lane shows proteins from an individual mouse. Migrations of ³⁵S-methionine–labeled apoB100 and apoB48 are indicated. (D) Bands corresponding to apoB100 and apoB48 were cut from the gel shown in C, and radioactivity was measured by scintillation counting. Two sets of experiments were combined for the final results (n = 7–9 mice per group). ***P < 0.001, by Student’s t test. (E) Autoradiogram of SDS-polyacrylamide gel showing newly synthesized ³⁵S-labeled proteins in cell lysates and media fractions of primary hepatocyte cultures. Migrations of ³⁵S-labeled apoB100 and apoB48 are indicated (n = 3 different hepatocyte cultures from 1 mouse of each genotype). (F) Bands corresponding to apoB100 and apoB48 were cut from the gel shown in E, and radioactivity was quantified by scintillation counting. The left panel shows results from the media fraction (Media) and the right panel from the cell lysate fraction (Cell). Results were normalized to the mean values from control samples, which were set to 100% (n = 3 different hepatocyte cultures from 1 mouse of each genotype). *P < 0.05 and **P < 0.01, by Student’s t test. In panels B, D, and F, the values for individual mice are shown, with longer horizontal bars indicating the mean and vertical bars indicating the SEM. Mice used were 4 months of age.