SELECTIVE PLANTING OF CATIONIZED, HAPTENIZED OVALBUMIN ON THE RAT TUBULAR BASEMENT-MEMBRANE

We developed an experimental protocol for planting exogenous antigens with different molecular weights and charges on the constituents of th e renal tubulointerstitium. The cationized antigens were injected sele ctively into the left renal arteries of Wistar rats. Antigen localizat ion was documented by immunohistochemistry on frozen sections. Cationi zed bovine serum albumin (BSA; 68 kDa, isoelectric point =9.5) localiz ed almost exclusively along the glomerular capillary wall. After appli cation of highly cationic polyethyleneimine, cationized BSA given subs equently was found in a linear distribution along the glomerular capil lary wall and along the peritubular capillaries. The fate of highly ca tionized ovalbumin conjugated with trinitrophenol (TNP-OA), subjected to gel filtration to obtain monomers (42 kDa, isoelectric point >10) d iffered; it was deposited in a linear pattern on the tubular basement membrane (TBM) and Bowman's capsule, and remained up to 36 h after inj ection. Noncationized, monomeric TNP-OA (42 kDa, isolectnic point =4.6 ) showed fine granular deposition in the tubular epithelium exclusivel y. These findings indicate that the barrier of the glomerular BM acts selectively on antigens with different molecular weights. They either settle on the peritubular capillaries, after passing the glomerular, o r reach the urinary space, after which they are reabsorbed by the tubu lar epithelial cells to reach the TBM.