C. Ejersted et al., HUMAN PARATHYROID HORMONE(1-34) INCREASES BONE-FORMATION AND STRENGTHOF CORTICAL BONE IN AGED RATS, European journal of endocrinology, 130(2), 1994, pp. 201-207
The effect of parathyroid hormone (PTH(1-34)) on mid-diaphyseal femora
l cortical bone was studied in 2-year-old male rats. The rats were tre
ated with daily injections of 15 nmol/kg PTH(1-34) or vehicle for 56 d
ays, and labelled with tetracycline and calcein on day 15 and day 40,
respectively. The PTH(1-34) treatment did not affect the body weights
or the lengths of the femora. Fluorescence microscopy showed large int
racortical cavities in the old vehicle-treated rats. After PTH treatme
nt, double labelling and new bone formation filling in these cavities
were found. Furthermore, an increased bone formation rate was observed
both at the periosteum and at the endosteum. This resulted in an incr
ease in the cross-sectional area and a decrease in the medullary area.
Three-point bending analysis revealed an increase in ultimate load, u
ltimate stiffness, energy absorption and ultimate stress after the PTH
(1-34) treatment. No differences were found between the groups regardi
ng the hydroxyproline concentration or apparent and real densities. Th
e ash concentration was, however, slightly reduced after PTH(1-34) tre
atment. The PTH(1-34) treatment of old rats induced the formation of b
one both from the periosteum and endosteum, with a pronounced filling
in of intracortical cavities, and, furthermore, a marked increase in t
he biomechanical competence of the cortical bone.