Defining a noncarcinogenic dose of recombinant human parathyroid hormone 1-84 in a 2-year study in Fischer 344 rats.
The carcinogenic potential of human parathyroid hormone 1-84 (PTH) was assessed by daily subcutaneous injection (0, 10, 50, 150 microg/kg/day) for 2 years in Fischer 344 rats. Histopathological analyses were conducted on the standard set of soft tissues, tissues with macroscopic abnormalities, selected bones, and bones with abnormalities identified radiographically. All PTH doses caused widespread osteosclerosis and significant, dose-dependent increases in femoral and vertebral bone mineral content and density. In the mid-and high-dose groups, proliferative changes in bone increased with dose. Osteosarcoma was the most common change, followed by focal osteoblast hyperplasia, osteoblastoma, osteoma and skeletal fibrosarcoma. The incidence of bone neoplasms was comparable in control and low-dose groups providing a noncarcinogenic dose for PTH of 10 microg/kg/day at a systemic exposure to PTH that is 4.6-fold higher than for a 100 microg dose in humans. The ability of PTH to interact with and balance the effects of both the PTH-1 receptor and the putative C-terminal PTH receptor, may lead to the lower carcinogenic potential observed with PTH than reported previously for teriparatide.
Jolette
Jacquelin
J
Charles River Laboratories, Senneville, Quebec H9X 3R3, Canada. jacquelin.jolette@ca.crl.com
Wilker
Clynn E
CE
Smith
Susan Y
SY
Doyle
Nancy
N
Hardisty
Jerry F
JF
Metcalfe
Anna J
AJ
Marriott
Thomas B
TB
Fox
John
J
Wells
David S
DS
D000818:Animals; D019540:Area Under Curve; D015519:Bone Density / Q000187:drug effects; D001859:Bone Neoplasms / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000473:pathology; D003720:Densitometry; D005260:Female; D005354:Fibrosarcoma / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D006965:Hyperplasia / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000473:pathology; D007279:Injections, Subcutaneous; D008297:Male; D018215:Osteoblastoma / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000473:pathology; D010006:Osteoblasts / Q000187:drug effects / Q000473:pathology; D012516:Osteosarcoma / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000473:pathology; D010026:Osteosclerosis / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000473:pathology; D010281:Parathyroid Hormone / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000633:toxicity*; D011859:Radiography; D051381:Rats; D011916:Rats, Inbred F344; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000633:toxicity; D012737:Sex Factors
D010281:Parathyroid Hormone; D011994:Recombinant Proteins