[Physiopathology of proteinuria and of renal regulation of the metabolism of circulating proteins].

The glomerular filtration of circulating proteins takes place at the level of the slit membrane where a porous structure, which limits or halts the passage of protein molecules of medium size, has been singled out. The small proteins, and among them many proteic hormones, are filtered, reabsorbed, and, to a great extent, catabolized by the tubular epithelia by means of at least partly selective mechanisms. Besides producing proteinuria, glomerular hyperpermeability, which does not modify the metabolism of microproteins, exposes to tubular catabolism a non-measurable quota of medium-sized nolecules whose survival in circulation is thus abbreviated. Reduced glomerular permeability does not influence the metabolism of medium-sized molecules, but reduces the catabolism of microproteins which are retained in the blood, a fact which is biologically very important. The clinical consequences of this retention have not yet been investigated.