Enhanced uptake of modified LDL in ob/ob versus WT mouse peritoneal macrophages is mediated by increases in cell surface expression of CD36 and SR-A. (A–C) [¹²⁵I,³H]acLDL cell association (A), degradation (B), and cholesteryl ester formation (C) are higher in ob/ob than in WT macrophages following acLDL loading. One representative experiment of three independent experiments each using pooled macrophages from five WT and seven ob/ob mice is shown. Short-term treatment (5 hours) of macrophages with either insulin or leptin does not change these parameters. C → CE (vertical axis, C), cholesterol to cholesteryl ester. (D) Protein expression of scavenger receptors CD36 and SR-A is increased while SR-BI expression is decreased in ob/ob versus WT macrophages, as determined by Western analysis (left). Protein extracts were prepared from pooled macrophages of five WT and five ob/ob mice. One experiment representative of four independent experiments is shown. CD36 and SR-A mRNA was not upregulated in ob/ob versus WT macrophages, as shown by Northern analysis (right). Northern analysis was performed with random-primed CD36, SR-A, and actin cDNA probes using total RNA isolated from pooled macrophages of ten mice of each strain. One experiment representative of three independent experiments is shown. (E) Specific binding of oxLDL to ob/ob macrophages is elevated. (F) Effects of fucoidan and anti-CD36 antibody on oxLDL binding to ob/ob and WT macrophages. [¹²⁵I]oxLDL binding assays were performed with pooled macrophages isolated from five mice of each strain, preincubated with the SR-A ligand fucoidan (20 μg/ml), mouse anti–CD36 IgA (20 μg/ml), or mouse control IgA (20 μg/ml, not shown). The decreases in total oxLDL binding in the presence of CD36 IgA or fucoidan were considered as binding mediated by CD36 or SR-A, respectively. CD36 contributes more to the increase in oxLDL binding to ob/ob versus WT macrophages than SR-A. One experiment representative of three independent experiments is shown. CD36-depend. and SR-A depend., oxLDL binding mediated by CD36 and SR-A, respectively.