Physiological doses of calcium regulatory hormones do not normalize bone cells in uraemic rats

Abstract

The results show that administration of PTH and calcitriol in doses that raise serum calcium fails to normalize the percentage of osteoclast surface, but was effective in raising osteoblast number and osteoblast volume in experimental renal failure. The results argue for abnormal response of bone cells to calcium-regulating hormones and/or the action of factors other than calcium regulatory hormones in the genesis of skeletal abnormalities of renal failure.

Downregulation of parathyroid hormone receptor gene expression and osteoblastic dysfunction associated with skeletal resistance to parathyroid hormone in a rat model of renal failure with low turnover bone

“…Studies conducted to date using Nx combined with parathyroidectomy and PTH infusion [11,12] did not provide direct data of bone turnover. Moreover, the model of Szabo et al [13] manifested osteomalacia, a pathological condition different from ABD. Referring to these past studies, we tried various PTH infusion rates and diet compositions, and succeeded in developing a novel experimental model for studying ABD, using a PTH infusion rate of 0.1 mg/kg/h (the same as that used by Szabo et al [12]) with a diet containing 2% calcium and 1% phosphorus.…”

Adverse effects of hyperphosphatemia on myocardial hypertrophy, renal function, and bone in rats with renal failure

“…This is the first study to address the role of dietary phosphorus and hyperphosphatemia in bone remodeling through histomorphometry. Szabó [20] performed an experimental study that evaluated whether physiologic doses of either PTH or calcitriol were able to normalize osteoclast and osteoblast function in uremic rats. The authors found that administration of PTH and calcitriol, in physiologic doses that raised calcium serum levels, failed to normalize the percentage of osteoclast surface.…”

Calciotropic hormones and the skeleton in uraemia

“…In this issue, Szabo et al . [12] use a somewhat specialized experimental model evaluating the effect of a combination of very short‐term, mild uraemia and the aparathyroid state (PTX)—with development of hypocalcaemia prevented by a high‐calcium diet—on the histomorphometry of cancellous bone. As the authors state, this is only a pilot study in which the effects of uraemia and PTX cannot be discriminated.…”

“…The pilot study of Szabo et al . [12], therefore, clearly focuses on the need for a much deeper understanding of the relationship between the known calciotropic hormones and bone cells in uraemia.…”

“…These results argue in favour of resistance of bone cells to the actions of PTH or to the combined actions of PTH and vitamin D in uraemia. The pilot study of Szabo et al [12], therefore, clearly focuses on the need for a much deeper understanding of the relationship between the known calciotropic hormones and bone cells in uraemia.…”