Rat hepatocytes were maintained in monolayer culture for 20 h in the presence of 10% (v/v) new-born calf serum and then for a further 1–24 h in serum-free medium containing 2 g bovine serum albumin/l. The specific binding of human 125-I-LDL to two distinct sites was then measured at 4°C. Binding to site 1 was displaced by dextran sulphate while that to site 2 was not. The presence of 1–100 nM insulin for 24 h in the second incubation significantly increased binding to site 1. Significant increases were also seen when cells were incubated with 10 nM insulin for 1 h. No significant effects of insulin on binding to site 2 were observed. In contrast, 10 nM—1 μM dexamethasone decreased binding to both sites. The effects of these hormones were mutually antagonistic.
