DISPOSITION OF OLIGONUCLEOTIDES IN ISOLATED-PERFUSED RAT-KIDNEY - INVOLVEMENT OF SCAVENGER RECEPTORS IN THEIR RENAL UPTAKE

The objective of this study was to clarify the renal disposition chara cteristics of a 20-mer model phosphodiester oligonucleotide and its pa rtially (PS3) and fully (PS) phosphorothioated derivatives, in isolate d rat perfused kidney. Venous outflow and urinary excretion patterns, as well as tissue accumulation of radioactivity after bolus injection of P-32-labeled oligonucleotides, were evaluated under both filtering and nonfiltering conditions. The binding affinity of oligonucleotides to bovine serum albumin in the perfusate increased as the number of su lfur atoms present in the oligonucleotide molecules increased, resulti ng in 21, 60 and 86% binding to bovine serum albumin for phosphodieste r oligonucleotide, PS, and PS, respectively. The apparent steady-state distribution volumes of the oligonucleotides, as calculated from the venous outflow patterns, were larger than that of inulin, which corres ponds to the extracellular volume of the kidney, suggesting their inte raction with tissue from the vascular space. PS showed the largest dis tribution volume. Urinary excretion of oligonucleotides was greatly re stricted, compared with that of inulin, which was used as a marker of glomerular filtration rate. The accumulation of these oligonucleotides was ascribed to both tubular reabsorption and uptake from the capilla ry side. The uptake of oligonucleotides from the capillary side increa sed as the number of sulfur atoms present in the molecules increased, suggesting sulfur atom-dependent interactions between oligonucleotides and renal tissue. In addition, the uptake of PS, was a saturable proc ess. Furthermore, coadministration of dextran sulfate and polyinosinic acid inhibited the renal uptake of PS,, whereas polycytidic acid and etamido-4'-isothiocyanato-stilbene-2,2'-disulfonic acid did not, sugge sting that oligonucleotides were taken up via the scavenger receptor-m ediated process for polyanions. These findings provide valuable inform ation for the development of delivery systems for antisense oligonucle otides.