[The cell-independent influence on calcification in living bone and in vitro (author's transl)].

Abstract

While there is no doubt that collagen is an important extra-cellular factor in the calcification of bone tissues, the exact nature of the process remains unclear. It has been explained in turn by the nucleation effect of corresponding lattice distances of apatite and collagen, that is, an oriented crystal overgrowth of the two substances which decreases the energy of nucleus formation, or by conformity between fibril-bundles and calciumphosphate crystal, or by the binding of phosphate to anionic positions of the collagen, as well as by the bone-forming effect of a non-collagen protein which is, however, separable from collagen. Because of their high viscosity proteo-polysaccharides inhibit crystal formation. Alkaline soluble proteo-pholysaccharides, however, appear to promote calcification in vitro and also in tissue of living bone. Lathyrogene and penicillamine impair the cross-linking in the bone collagen; this probably explains their disturbing effect on ossification. Diphosphonates would, like anorganic pyrophosphate, inhibit both the formation and dissolution of apatite crystal. Our research shows, however, that methanie-bis-phosphonate clearly promotes calcification, in vitro and in vivo. In vitro, and probably also in vivo, magnesium inhibits the formation of apatite crystal nucleus. Our research indicates moreover that magnesium also slows down the reduction of calcified bone tissue on account of its inhibiting effect on parathormone emission.