Calcitonin and the bone fluid compartment. Effect of calcitonin and/or parathyroid hormone on plasma radiocalcium changes

Journal Article · Thu Jan 01 04:00:00 EST 1976 · Clin. Orthop.; (United States)

OSTI ID:6543510

Doppelt, S H; Talmage, R V

Changes in plasma calcium and /sup 45/Ca concentrations were followed after injection of calcitonin or a combination of calcitonin (CT) and parathyroid hormone (PTH) into thyroparathyroidectomized rats maintained on thyroxine. Comparison was made between rats injected with the hormone(s) after a recent feeding and after an overnight fast. Also compared were plasma /sup 45/Ca changes when the radionuclide was injected 18 hr (18 hr /sup 45/Ca) before, and more than 6 days (> 6 day /sup 45/Ca) prior to hormone administration. The following results were obtained: The action of CT predominated over that of PTH for the first few hours after injection. However, the effects of PTH were eventually manifested even when additional CT was administered. In the ''> 6 day'' /sup 45/Ca groups. PTH normally produced an increase in plasma /sup 45/Ca specific activity. However, in fasted rats, plasma /sup 45/Ca fell with total calcium with no change in specific activity following CT injection. In fed rats CT injection was followed by a decrease in plasma /sup 45/Ca specific activity. When both hormones were administered plasma /sup 45/Ca specific activity changes mimicked those produced by CT alone even after PTH plasma effects were manifested. In the ''18 hr'' /sup 45/Ca groups, CT produced first a drop in plasma /sup 45/Ca, followed by a reduction in the rate of its removal from plasma. It is concluded that the data can best be explained by the postulate that plasma calcium concentrations are maintained by the control of fluxes between bone fluid in the osteocyte-lining cell bone unit and the extracellular fluid. PTH increases the efflux from this bone fluid compartment while CT restricts the source of calcium and, therefore, the efflux. Plasma /sup 45/Ca changes are due to a combination of changes in flux rates and mixing processes between the extracellular fluid compartment and the bone fluid compartment.

• Research Organization: Univ. of North Carolina School of Medicine, Chapel Hill
• OSTI ID: 6543510
• Journal Information: Clin. Orthop.; (United States), Journal Name: Clin. Orthop.; (United States) Vol. 118; ISSN CORPA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
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59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL MATERIALS
BLOOD
BLOOD PLASMA
BODY
BODY FLUIDS
BONE CELLS
BONE TISSUES
CALCITONIN
CALCIUM
CALCIUM 45
CALCIUM ISOTOPES
CONNECTIVE TISSUE
CONNECTIVE TISSUE CELLS
DAYS LIVING RADIOISOTOPES
ELEMENTS
EVEN-ODD NUCLEI
FEEDING
HORMONES
INTERMEDIATE MASS NUCLEI
ISOTOPES
MAMMALS
METALS
NUCLEI
ORGANIC COMPOUNDS
PEPTIDE HORMONES
PEPTIDES
POLYPEPTIDES
PROTEINS
RADIOISOTOPES
RADIONUCLIDE KINETICS
RATS
RODENTS
SOMATIC CELLS
THYROID HORMONES
TISSUES
VERTEBRATES