Quantitative Histochemistry of the Nephron. Vi. Hydroxyproline in the Human Glomerulus.

Staining reactions characteristic of collagen and reticulin are found in pathologically altered glomeruli (1, 2), and fibrils with the periodicity of collagen fibrils have been observed occasionally in electron micrographs of severely damaged glomerular tufts. However, as far as we are aware, fibrils have not been found by light or electron microscopy in the normal glomerular tuft, except at the hilus; and, in particular, no fibrils with the periodicity of collagen fibrils have been seen in the normal glomerular capillary basement membrane (3-6). Hydroxyproline estimations are widely used as a measure of collagen because no other known animal protein contains appreciable amounts of this amino acid (7, 8). Goodman, Greenspon and Krakower used sonic vibration to separate glomerular basement membrane from healthy canine glomeruli and found that the hydroxyproline content of their basement membrane preparations was 7 per cent (9). They suggested, therefore, that glomerular capillary basement membrane contained a considerable amount of collagen. As their results appeared to conflict with the morphological evidence, the hydroxyproline content of the human glomerulus was reinvestigated, using a microdissection and microassay technique in which glomerular tufts were dissected out intact and free of Bowman's capsules for hydroxyproline assay.