TRANSPORT OF PHOSPHOROTHIOATE OLIGONUCLEOTIDES IN KIDNEY - IMPLICATIONS FOR MOLECULAR THERAPY

The systemic administration of phosphorothioated antisense oligonucleo tides has been demonstrated to be an effective strategy for the contro l of gene expression. Because previous studies have suggested both hep atic and renal accumulation of systemically administered oligonucleoti des, we explored whether the kidney might be a site of free DNA transp ort. [P-32]-phosphorothioate oligonucleotides (20 mers) were excreted in urine but cleared at only 30% of glomerular filtration rate. Plasma clearance of the label was very rapid (t(1/2) similar to 5 min) but t he half life of labeled S-deoxynucleotide excreted in urine was much s lower (28 min). Infused oligonucleotide appeared in urine with little degradation. By autoradiography of renal tissue, labeled antisense oli gonucleotides appeared within Bowman's capsule and the proximal tubule lumen. DNA was detected in association with brush border membrane and within tubular epithelial cells. Brush border membrane preparations f rom rat kidney contained oligonucleotide binding proteins as determine d by gel mobility shift and UV cross linking assays. Because renal epi thelial cells efficiently take up phosphorothioate oligonucleotides wi thout apparent degradation, the kidney appears to be an excellent targ et for site-directed antisense therapy, but may be a site of antisense toxicity as well.