1. Skin fibroblast lines were cultured from nine patients who had the features of
idiopathic juvenile osteoporosis, six relatives, five unrelated control subjects and three unrelated patients with
osteogenesis imperfecta type I. Some patients with
idiopathic juvenile osteoporosis were adults whose previous
osteoporosis was in remission. Two patients with
idiopathic juvenile osteoporosis were siblings and one patient with
idiopathic juvenile osteoporosis had a daughter with severe
osteogenesis imperfecta (type III). 2. The ratio of type III to
type I collagen, synthesized by fibroblasts, was increased in two of the patients with
osteogenesis imperfecta type I and in the daughter with
osteogenesis imperfecta type III, but was normal in all the other patients with
idiopathic juvenile osteoporosis and the other relatives. 3. Radiolabelled
collagen was digested by
cyanogen bromide and separated on SDS-PAGE. Unreduced
collagen peptides migrated normally, except those from both the two siblings with
idiopathic juvenile osteoporosis. In these two lines, abnormal migration suggested the presence of
collagen I mutations. 4. The secretion of synthesized
collagen by these two
idiopathic juvenile osteoporosis lines and two others was reduced to only 43-45% as compared with a line from a 13-year-old control subject, which was defined as 100%. The three
osteogenesis imperfecta type I lines secreted 18-37%, the other five
idiopathic juvenile osteoporosis lines secreted 57-75%, the relatives (including the daughter with severe
osteogenesis imperfecta) secreted 49-115% and the controls secreted 69-102%.(ABSTRACT TRUNCATED AT 250 WORDS)