PHARMACOKINETIC ANALYSIS AND CELLULAR-DISTRIBUTION OF THE ANTI-HIV COMPOUND SUCCINYLATED HUMAN SERUM-ALBUMIN (SUC-HSA) IN-VIVO AND IN THE ISOLATED-PERFUSED RAT-LIVER

After intravenous injection of a low dose (25 mug/kg) in rats, the anti HIV-1 compound succinylated human serum albumin (Suc-HSA) is taken up mainly in the liver and spleen and is proteolytically degraded. Ten minutes after injection of I-125-Suc-HSA, 72 and 14% of the dose were found in the liver and spleen, respectively. With immunohistochemistry we demonstrated that in both organs, Suc-HSA was specifically endocytosed in endothelial cells. In the isolated perfused rat liver preparation, liver uptake was shown to be saturable, with a K(m) of 2.9 10(-8) M and a V(max) of 2.4 mug/min/100 g body weight. The apparent K(m) and V(max) in vivo were 2.2 10(-7) M and 10.3 mug/min/100 g, respectively. Uptake in liver and spleen was inhibited by preadministration of an excess of formaldehyde-treated albumin and with polyinosinic acid, indicating the involvement of the scavenger receptor, as anticipated for such polyanionic compounds. Suc-HSA is not absorbed intact from the colon and the ileum. After injecting (i.v.) rats with a high dose of Suc-HSA (10 mg/kg), the elimination t1/2 was 3 hr, and therefore, sustained plasma levels above the concentration needed for in vitro anti-HIV-1 activity can be achieved.