Relation of tubular interstitial disease to renal function.

In vitro concentrative transport of PAH-3H was evaluated in human renal biopsies by section freeze-dry autoradiography. Renal cortical tissue obtained by biopsy was incubated in vitro in medium containing PAH-3H, and section freeze-dry autoradiographs prepared. The autoradiographs demonstrated that the number of proximal tubules which accumulate PAH-3H in vitro varies inversely with the amount of tubular interstitial disease and directly with glomerular filtration rate. In order to further examine the mechanisms of tubular-interstitial disease, we have developed a technique for simultaneous fluorescent microscopy and autoradiography in single freeze-dried sections. This technique permits evaluation of the relationship between concentrative transport and immunoglobulin deposition in individual tubules and should increase our knowledge of the biologic significance of immunoglobulin deposits in proximal tubules.