Alteration in the Extent of Collagen I Hydroxylation,Isolated from Femoral Heads of Women with a Femoral Neck Fracture Caused by Osteoporosis

The aim of this study was to investigate the extent of lysyl and prolyl hydroxylation of collagen I in osteoporosis and compare it with collagen I from ``bone healthy' individuals. Collagen I was isolated from femoral heads of osteoporotic women, from women suffering from osteoarthrosis of the hip, and from healthy women 60–85 years of age. The femoral heads were dissected into compact and trabecular bone of the neck region and from trabecular bone of the head region, and collagen I was extracted by limited pepsin digestion. The amino acid analysis of individual α-chains showed a remarkably higher degree of hydroxylation of lysine residues both in the α1(I)- and in the α2(I)-chains in osteoporotic bone compared with osteoarthrotic and ``normal' bone, whereas the prolyl hydroxylation was nearly unchanged. The lysyl overhydroxylation was observed in the compact as well as in the trabecular bone of osteoporotic femoral heads. These biochemical alterations may play a crucial role in the pathogenesis of osteoporosis. Received: 2 May 1996 / Accepted: 31 December 1996