Studies on glomerular permeability using inert polymers.

Dextrans and other macromolecular inert polymers such as polyvinyl pyrrolidone fulfil all the criteria of an ideal test material for measuring glomerular permeability. Following a single intravenous injection of radioactively labelled polydisperse material serial plasma and urine samples can be analysed by gel filtration chromatography and the polymer fractionated into its constituent molecular sizes. Polymer of molecular size 24 A is capable of passing through the glomerulus as readily as water while material larger than 60 A is affectively excluded from the glomerular filtrate and one can determine the clearance of 20--30 intermediate molecular sized fractions. The accumulated data can be analysed by a number of different theoretical mathematical models; furthermore the technique can be employed in the study of proteinuria induced by vasoactive amines such as renin or angiotensin.