[Effect of intermittent administration of human PTH on experimental osteopenia in adult rat: a histomorphometric study of both trabecular and cortical bone of the vertebrae].

Both the cancellous and the cortical envelopes of the vertebral bone of osteopenic rats were histomorphometrically evaluated to elucidate the effect of an intermittent administration of h-PTH (1-34) on bone remodeling. Seven-eight-month-old female Wistar rats were used, and osteopenia was produced by ovariectomy, by prednisolone administration, or by streptozotocin-induced diabetes mellitus. The rats were divided into 10 groups; as base line control rats, vehicle administered rats, and h-PTH administered rats for each of the three kinds of osteopenia, and sham operated rats. Vehicle or h-PTH was administered subcutaneously six times a week from the 9th to the 12th week of the experiment. The dosage of h-PTH was 6.0 micrograms/kg. Ovariectomy developed a high turn-over osteopenia, and prednisolone administration and diabetes mellitus caused a low turn-over osteopenia. All 3 kinds of osteopenia showed similar changes in histomorphometric parameters after h-PTH treatment. In the cancellous envelope, the bone volume increased significantly in all groups. The trabecular thickness, osteoid surface, mineralizing surface, mineral apposition rate, and the bone formation rate increased in all groups after the treatment with h-PTH. The eroded surface significantly decreased except in the diabetes mellitus rats. In the endocortical envelope, the osteoid surface, mineralizing surface and the mineral apposition rate increased in all groups. The eroded surface significantly decreased in all groups after the treatment with h-PTH. The cortical thickness significantly increased except in the ovariectomized rats. The results of the present study suggested that an intermittent administration of h-PTH stimulated bone formation without increasing bone resorption in all three kinds of osteopenia induced by ovariectomy, corticosteroid, or diabetes mellitus.