Biomaterial Database

Bone and plasma calcium homeostasis. 1987

A M Parfitt

Henry Ford Hospital, Bone and Mineral Research Laboratory, Detroit, MI 48202.

Regulation of plasma free calcium concentration displays the following features: (1) The level in an individual varies within fairly narrow limits and is characterized by a mean (an estimate of the individual set point) and a standard deviation (an estimate of oscillation about the set point). (2) There is an intrinsic circadian oscillation that is independent of external disturbing signals. (3) Individual values (set points) are partly under genetic control with significant between-family differences. (4) Correction of errors is rather slow-it usually takes at least 12 hours to restore the basal level after experimental induction of hyper- or hypocalcemia. (5) Correction of errors can occur with normal efficiency in the absence of parathyroid hormone or calcitonin, provided the system is adequately primed with some form of vitamin D. These and other facts are best explained by a concept that locates the calcium homeostatic system at the quiescent bone surface. Across this cellular and tissue barrier exchange of calcium between blood and bone in the absence of net flux can be demonstrated by autoradiography. The distinction between the homeostatic system and the remodeling system that regulates bone mass is not absolute, since the latter can participate in short term correction of errors, and if the obligatory calcium loss (determined by the difference between the plasma calcium set point and the threshold for renal tubular reabsorption of calcium) is too high to be satisfied by net intestinal absorption, the remodeling system must make up the difference by sacrificing bone.(ABSTRACT TRUNCATED AT 250 WORDS)

UI	MeSH Term	Description	Entries
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D010281	Parathyroid Hormone	A polypeptide hormone (84 amino acid residues) secreted by the PARATHYROID GLANDS which performs the essential role of maintaining intracellular CALCIUM levels in the body. Parathyroid hormone increases intracellular calcium by promoting the release of CALCIUM from BONE, increases the intestinal absorption of calcium, increases the renal tubular reabsorption of calcium, and increases the renal excretion of phosphates.	Natpara,PTH (1-84),PTH(1-34),Parathormone,Parathyrin,Parathyroid Hormone (1-34),Parathyroid Hormone (1-84),Parathyroid Hormone Peptide (1-34),Hormone, Parathyroid
D001842	Bone and Bones	A specialized CONNECTIVE TISSUE that is the main constituent of the SKELETON. The principal cellular component of bone is comprised of OSTEOBLASTS; OSTEOCYTES; and OSTEOCLASTS, while FIBRILLAR COLLAGENS and hydroxyapatite crystals form the BONE MATRIX.	Bone Tissue,Bone and Bone,Bone,Bones,Bones and Bone,Bones and Bone Tissue,Bony Apophyses,Bony Apophysis,Condyle,Apophyses, Bony,Apophysis, Bony,Bone Tissues,Condyles,Tissue, Bone,Tissues, Bone
D001861	Bone Regeneration	Renewal or repair of lost bone tissue. It excludes BONY CALLUS formed after BONE FRACTURES but not yet replaced by hard bone.	Osteoconduction,Bone Regenerations,Regeneration, Bone,Regenerations, Bone
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D004002	Clodronic Acid	A diphosphonate which affects calcium metabolism. It inhibits bone resorption and soft tissue calcification.	Clodronate,Dichloromethylene Diphosphonate,Bonefos,Cl2MDP,Clodronate Disodium,Clodronate Sodium,Dichloromethane Diphosphonate,Dichloromethanediphosphonate,Dichloromethanediphosphonic Acid,Dichloromethylene Biphosphonate,Dichloromethylenebisphosphonate,Acid, Clodronic,Acid, Dichloromethanediphosphonic,Biphosphonate, Dichloromethylene,Diphosphonate, Dichloromethane,Diphosphonate, Dichloromethylene,Disodium, Clodronate,Sodium, Clodronate
D004164	Diphosphonates	Organic compounds which contain P-C-P bonds, where P stands for phosphonates or phosphonic acids. These compounds affect calcium metabolism. They inhibit ectopic calcification and slow down bone resorption and bone turnover. Technetium complexes of diphosphonates have been used successfully as bone scanning agents.	Bisphosphonate,Bisphosphonates
D006706	Homeostasis	The processes whereby the internal environment of an organism tends to remain balanced and stable.	Autoregulation
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man