A comparison of the effects of parathyroid hormone and parathyroid hormone-related protein on osteocalcin in the rat.
We compared the effects of parathyroid hormone (PTH1-34) and parathyroid hormone-related protein (PTHrp1-34) 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 PTHrp1-34. Chronic administration of PTH1-34 or PTHrp1-34 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.
Gundberg
C M
CM
Department of Orthopaedics, Yale University School of Medicine, New Haven, Connecticut, USA.
Fawzi
M I
MI
Clough
M E
ME
Calvo
M S
MS
D000704:Analysis of Variance; D000818:Animals; D003198:Computer Simulation; D000242:Cyclic AMP / Q000378:metabolism; D006614:Hindlimb / Q000187:drug effects / Q000378:metabolism; D006934:Hypercalcemia / Q000139:chemically induced; D017674:Hypophosphatemia / Q000139:chemically induced; D066298:In Vitro Techniques; D015918:Infusion Pumps, Implantable; D008297:Male; D015675:Osteocalcin / Q000097:blood* / Q000378:metabolism; D010281:Parathyroid Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D044162:Parathyroid Hormone-Related Protein; D016105:Parathyroidectomy; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology*; D010477:Perfusion; D011506:Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D019379:Teriparatide
D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D011506:Proteins; D015675:Osteocalcin; D019379:Teriparatide; D000242:Cyclic AMP