A comparison of the effects of parathyroid hormone and parathyroid hormone-related protein on osteocalcin in the rat

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Abstract
We compared the effects of parathyroid hormone (PTH1–34) and parathyroid hormone‐related protein (PTHrpl–34) on osteocalcin release in the isolated rat hindlimb and in intact and thyroparathyroidectomized (TPTX) rats. PTH1–34 suppressed osteocalcin release from perfused rat hindquarters, while PTHrp1–34 had no effect on osteocalcin release, despite comparable stimulation of cAMP production. Similarly, serum osteocalcin declined in the intact and TPTX animals by 5 h after a single dose of PTH1–34, while there was no response to PTHrpl–34. Chronic administration of PTH1–34 or PTHrpl–34 produced comparable hypercalcemia and hypophosphatemia in sham‐operated and TPTX animals. Chronic PTH1–34 administration produced significant increases in serum osteocalcin both in the sham‐operated rats and in the TPTX animals. However, in animals chronically treated with PTHrp1–34, there was no change at any time point in osteocalcin in either sham‐operated or TPTX rats. These differences could be inherent or merely due to potency differences between the two peptides.
Funding Information
  • NIH (RO1-AR38460)
  • RESEARCH CAREER DEVELOPMENT award (AR01789)

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