Stimulation by parathyroid hormone of sup 45 Ca sup 2+ uptake in osteoblast-like cells: Possible involvement of alkaline phosphatase

Journal Article · Sun Apr 01 04:00:00 EDT 1990 · Endocrinology; (USA)

DOI:https://doi.org/10.1210/endo-126-4-1941· OSTI ID:7118087

Fukayama, S; Tashjian, Jr, A H ^[1]

---

1. Harvard School of Public Health, Boston, MA (USA)

We have investigated the actions of human PTH (hPTH-(1-34)) on the association of 45Ca2+ with two human (SaOS-2 and MG-63) and two rat (ROS 17/2.8 and UMR-106) osteoblast-like cell types. In SaOS-2 cells, hPTH-(1-34) binds to specific membrane receptors to activate adenylate cyclase. Treatment of SaOS-2 cells with hPTH-(1-34) resulted in an increase in 45Ca2+ uptake, in a dose-dependent fashion, up to 2- to 4-fold above control values. The increase was first evident at 10 min and persisted for at least 30 min. Treatment with nimodipine, a calcium channel antagonist, was without effect on the stimulatory action of PTH. A similar enhancement of cell-associated 45Ca2+ was observed when the cells were incubated with vasoactive intestinal peptide, which acts via different receptors to activate adenylate cyclase in SaOS-2 cells. Treatment with (Bu)2cAMP also induced an increase in cell-associated 45Ca2+. Pretreatment of SaOS-2 cells with hPTH-(1-34) for 4 h, which induced homologous desensitization to a second challenge with the same peptide for stimulation of cAMP production, did not attenuate the further enhancement of cell-associated 45Ca2+ by a second treatment with hPTH-(1-34). We then examined a possible relationship between alkaline phosphatase (ALPase) and 45Ca2+ uptake. SaOS-2 cells contained high levels of alkaline phosphatase activity and continuously released the enzyme into the medium. Release was enhanced by treatment with hPTH-(1-34) for 10 min. Incubation of cells with levamisole (an inhibitor of the liver/bone/kidney type of ALPase) resulted in a rapid decrease in basal and PTH-stimulated 45Ca2+ uptake, while treatment with L-Phe-Gly-Gly was without effect. Treatment of the cells with ALPase (bovine kidney) enhanced 45Ca2+ uptake. In MG-63 cells, a stimulatory effect of hPTH-(1-34) on cell-associated 45Ca2+ was also observed; however, hPTH-(1-34) did not stimulate cAMP production in MG-63 cells.

• OSTI ID: 7118087
• Journal Information: Endocrinology; (USA), Journal Name: Endocrinology; (USA) Vol. 126:4; ISSN ENDOA; ISSN 0013-7227
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ALKALINE PHOSPHATASE
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BONE CELLS
CALCIUM 45
CALCIUM COMPOUNDS
CALCIUM ISOTOPES
CONNECTIVE TISSUE CELLS
CYCLASES
DAYS LIVING RADIOISOTOPES
DOSE-RESPONSE RELATIONSHIPS
ENZYME ACTIVITY
ENZYMES
ESTERASES
EVEN-ODD NUCLEI
HORMONES
HYDROLASES
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LYASES
MAMMALS
MAN
MEMBRANE PROTEINS
MEMBRANE TRANSPORT
NUCLEI
ORGANIC COMPOUNDS
PARATHORMONE
PEPTIDE HORMONES
PEPTIDES
PHOSPHATASES
PRIMATES
PROTEINS
RADIOISOTOPES
RATS
REACTION KINETICS
RECEPTORS
RODENTS
SOMATIC CELLS
TRACER TECHNIQUES
TUMOR CELLS
VERTEBRATES