Studies on the mechanisms underlying the transfer of calcium and phosphate from bone to blood

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1978

DOI:https://doi.org/10.2172/6802123· OSTI ID:6802123

Brommage, Jr., Robert J. ^[1]

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1. Univ. of Rochester, NY (United States)

The skeleton is recognized as a crucial organ in the minute-to-minute regulation of the blood levels of calcium and phosphate. The fluxes of calcium and phosphate to and from bone greatly exceed the entry and exit of these ions occurring in the intestine and kidneys. Parathyroid hormone, calcitonin, and 1,25-dihydroxyvitamin D₃ (1,25-(OH)₂D₃ are known to influence the transfer of calcium and phosphate from bone to blood. Three mechanisms have been proposed to explain the hormonal control of the calcium and phosphate effluxes from bone. The concept of a bone membrane maintaining a distinct bone extracellular fluid composition has led to the pump and pH gradient theories. An alternate solubilizer theory proposes that bone cells secrete a substance which increases the solubility of the bone mineral. The bone membrane concept was originally proposed to explain the presence of the apparent anomalously high concentrations of potassium in the bone extracellular fluid. However, the available evidence does not allow an unambiguous decision concerning the presence of a bone membrane. Calvarial lactate production was unaltered by 1,25-(OH)₂D₃ treatment and consequently 1,25-(OH)₂D₃ does not appear to promote the mobilization of bone mineral through a lactate-mediated pH gradient mechanism. 1,25-(OH)₂D₃ did increase the solubility of non-vital bone, clearly demonstrating that the solubilizer mechanism is at least partially responsible for the mobilization of bone mineral and the regulation of blood levels of calcium and phosphate. Vitamin D-deficient female rats fed a 0.2% calcium, 0.4% phosphorous diet and supplemented with daily injections of 0.75 pmole of 1,25-(OH)₂D₃ were shown to be capable of bearing young. When the injections of 1,25-(OH)₂D₃ were terminated at delivery, the dams and pups showed signs of vitamin D deficiency approximately one week later.

• Research Organization: Univ. of Rochester, NY (United States). Dept. of Radiation Biology and Biophysics
• Sponsoring Organization: USDOE
• DOE Contract Number: EY-76-C-02-3490
• OSTI ID: 6802123
• Report Number(s): UR--3490-1468
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
60 APPLIED LIFE SCIENCES
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
ANIONS
BIOLOGICAL EFFECTS
BIOLOGICAL MATERIALS
BIRDS
BLOOD
BODY
BODY FLUIDS
CALCITONIN
CALCIUM COMPOUNDS
CATIONS
CHARGED PARTICLES
CHICKENS
CHOLECALCIFEROL
FOWL
HORMONES
IONS
ISOTOPE APPLICATIONS
MAMMALS
NEONATES
NUTRITIONAL DEFICIENCY
ORGANIC COMPOUNDS
ORGANS
OXYGEN COMPOUNDS
PARATHORMONE
PEPTIDE HORMONES
PEPTIDES
PHOSPHATES
PHOSPHORUS COMPOUNDS
POLYPEPTIDES
PROTEINS
RATS
RODENTS
SKELETON
TRACER TECHNIQUES
TRANSLOCATION
VERTEBRATES
VITAMIN D
VITAMINS