Rat high density lipoprotein subfraction (HDL3) uptake and catabolism by isolated rat liver parenchymal cells.

摘要: Abstract Rat liver parenchymal cell binding, uptake, and proteolytic degradation of rat 125I-labeled high density lipoprotein (HDL) subfraction, HDL3 (1.10 less than d 1.210 g/ml), in which apo-A-I is the major polypeptide, were investigated. Structural metabolic integrity isolated cells was verified by trypan blue exclusion, low lactic dehydrogenase leakage, expected morphology, gluconeogenesis from lactate pyruvate. incubated with 10 X 10(6) at 37 degrees 4 albumin Krebs-Henseleit bicarbonate buffer, pH 7.4. Binding uptake determined radioactivity washed cells. Proteolytic trichloroacetic acid-soluble incubation medium. At degrees, maximum binding (Bmax) occurred 30 min a Bmax 31 ng/mg dry weight The apparent dissociation constant receptor system (Kd) 60 10(-8) M, based on Mr = 28,000 apo-A-I, predominant protein. showed 15-min lag then proteolysis. After 2 hours 5.8% degraded. Sixty per cent trypsin-releasable. presence varying concentrations native (cold) HDL3, very lipoproteins, lipoproteins. Incubation resulted greatest inhibition degradation. When preincubated increasing amounts antiserum, decreased to complete inhibition. Cell markedly diminished degrees. Less 1 mM chloroquine enhanced proteolysis but 5 or greater, inhibited accumulation L-[U-14C]Lysine-labeled bound, taken up, degraded as effectively HDL3. These data suggest that are actively performed linked sequence:binding, finally Furthermore, there may be specific (lipoprotein A) recognition site(s) plasma membrane. Finally, our further support previous reports important role lysosomes