[Effect of h-PTH on bone and bone marrow tissue in experimental osteopenia in rat]

We have evaluated changes in bone volume, bone marrow tissue, and the density of osteoclasts caused by intermittent administration of human parathyroid hormone (h-PTH) to experimental osteopenia induced in rat by ovariectomy (OVX) or by diabetes mellitus (use of streptozotocin: STZ). A bone and marrow histomorphometric study was performed on HE-stained and tartrate-resistant acid phosphatase-stained (TRAP-stain) tibial bone sections. Retired Wistar rats, 7-8 months old, were used. They were separated into the following nine groups; sham operated, base line control, vehicle administered, low or high dosage h-PTH administered OVX and STZ groups. 6.0 micrograms/kg/day of h-PTH (1-34) as a low dosage, and 60.0 micrograms/kg/day as a high dosage, was injected subcutaneously six times a week for 4 weeks from 9 weeks after ovariectomy or injection of streptozotocin. The bone volume decreased in both the OVX and STZ groups, while the fat tissue volume increased in the bone marrow in the OVX groups to compensate for this decrease, and the foamy marrow tissue volume increased in the STZ groups. The bone volume and the mean trabecular thickness in both the OVX and STZ groups increased by the intermittent administration of h-PTH, while the TRAP positive trabecular surface and the number of osteoclasts decreased. There was no significantly different bone changes between the low and high dosage groups. It is thought that the TRAP positive trabecular surface represented not only the active bone resorption surface but also the related contiguous uneroded surface.