Binding and endocytosis of apo- and holo-lactoferrin by isolated rat hepatocytes.

摘要: We characterized binding and endocytosis of 125I-bovine lactoferrin by isolated rat hepatocytes. Iron-depleted (apo-Lf), approximately 30% saturated (Lf), iron-saturated (holo-Lf) were used. At 4 degrees C, cells bound 125I-apo-Lf 125I-holo-Lf with nearly identical apparent first order kinetics (t1/2 = 42 min). Holo-Lf apo-Lf competed each other for binding. Hepatocytes optimally at pH greater than or equal to 7 but poorly less 6. Ca2+ (greater 100 microM) enhanced Lf cells, holo-Lf remained monomeric present as determined gel filtration chromatography. With Ca2+, exhibited 10(6) high affinity sites (Kd 20 nM) 10(7) low 700 both apo- holo-Lf. Without the component only. EGTA dextran sulfate together released 90% 125I-Lf prebound individually removed separate populations surface-bound 125I-Lf. Cells in a Ca(2+)-dependent manner present. conclude that not require Ca2+; only are sulfate-sensitive. Neither transferrin nor asialo-orosomucoid blocked Some cationic proteins others inhibited 37 hepatocytes endocytosed similarly, hyperosmolality 500 mmol/kg) uptake 90%. These data support proposal regulate blood concentration receptor-mediated endocytosis.