Bovine parathyroid tissue: a model to compare the biosynthesis and secretion of parathyroid hormone and parathyroid hormone-related peptide.
Bovine parathyroid tissue was evaluated as a model to compare parathyroid hormone-related peptide (PTH-rP) and parathyroid hormone (PTH) secretion. Tissue was incubated in variable calcium levels (n = 5). A parathyroid cell digest was prepared from collagenase-treated glands. PTH-rP and PTH levels were determined by radioimmunoassay. PTH-rP bioactivity was determined by 3H-cAMP production in a UMR 106 cell bioassay. PTH-rP levels in the incubation medium were 2.0 ng/mg protein (0.25 mmol Ca++), 2.2 ng/mg protein (1.25 mmol Ca++), and 1.9 ng/mg protein (2.5 mmol/L Ca++). PTH levels were 321 ng/mg protein (0.25 mmol/L Ca++) and 200 ng/mg protein (2.5 mmol Ca++). Therefore, calcium significantly inhibited PTH but not PTH-rP secretion (p = 0.03). Addition of incubation medium to the bioassay resulted in 3H-cAMP levels that were 8 to 10 times greater than basal levels. Greater than 50% of the activity persisted after addition of PTH antibody, demonstrating that a significant amount of the activity was caused by PTH-rP. Tissue PTH-rP was 5.1 ng/mg protein, compared with 2080 ng/mg protein for PTH. We conclude that (1) bovine parathyroid tissue contains bioactive PTH-rP and is a useful model to compare the biosynthesis and secretion of PTH-rP and PTH in normal tissue and (2) unlike PTH, PTH-rP secretion is not regulated by calcium.
Connor
C S
CS
Department of Surgery, Leavenworth Veterans Administration Medical Center, Kan. 66048.
Drees
B M
BM
Thurston
A
A
Forte
L
L
Hermreck
A S
AS
Hamilton
J W
JW
D000818:Animals; D001681:Biological Assay; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D000242:Cyclic AMP / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000378:metabolism / Q000494:pharmacology; D012516:Osteosarcoma; D010280:Parathyroid Glands / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000096:biosynthesis* / Q000378:metabolism / Q000494:pharmacology; D044162:Parathyroid Hormone-Related Protein; D051381:Rats; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism
D009363:Neoplasm Proteins; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D000242:Cyclic AMP; D002118:Calcium