Effect of inhibited endocytosis in sinusoidal liver cells on catabolism of equine haptoglobin and haemoglobin in the hen.

Catabolism of equine haptoglobin (Hp), haptoglobin-haemoglobin complex (Hp-Hb) and haemoglobin (Hb) in the hen was studied in the liver reticuloendothelial system (RES) in which endocytosis of protein was inhibited by aggregated denatured albumin (Agr-Alb). Intravenous injection of Agr-Alb together with equine [125I]Hp, [125I]Hp-Hb or [125I]Hb partially inhibited elimination of these proteins from hen circulation. The decrease of clearance was less pronounced when the labelled proteins were introduced 30 min after Agr-Alb injection due to stimulation of phagocytosis in RES by Agr-Alb. Elimination of equine proteins (Hp, Hp-Hb and Hb) from hen circulation by RES is only one of the possible metabolic fates of these proteins.