Bone & mineral metabolism
1. Bone structure & metabolism
i) organic matrix : type I collagen(90-95%)
noncollagenous portion of the organic matrix
: albumin & ¥á2-HS glycoproteins ±â¿ø protein
¥á-carboxyglutamic acid(GLA)[bone GLA protein=BGP, osteocalcin
& matrix GLA protein], glycoprotein osteonectin,
phosphoprotein osteopontin, sialoproteins, thrombospondinµîÀÇ ´Ü¹é
ii) mineral phase : Ca, P, crystalline hydroxyapatite
* osteoblast: TGF-¥â type I, II, acidic fibroblast growth factor(aFGF)
basic fibroblast GF(bFGF), PDGF, IGF-I, II¿Í °°Àº growth factor°¡ stimulation
* osteoclast
2. Calcium metabolism 1-2 kg >98% skeleton
normal: 8.8 - 10.4 mg/dL
* 3 forms i) free ions
ii) plasma protein°ú °áÇÕ
iii) diffusible complex
protein-bound Ca = 0.8¡¿Alb + 0.2¡¿globulin + 3
* corrected Alb°è»ê¹ý
s-Alb level < 4.0 g/dL¿¡¼ Alb 1g/dL´ç s-Ca 1mg/dL¾¿ º¯È
¿¹> s-Ca = 7.8, s-Alb =3.0À̶ó¸é
corrected Ca = 8.8 mg/dL
* Ca source
intestinal tractÀ¸·ÎºÎÅÍ Èí¼ö(¡100-200 mg/d)
bone mineral·Î ºÎÅÍÀÇ ÀçÈí¼ö(¡100 mg/d)¿¡ ÀÇÇØ plasma·Î À¯ÀԵȴÙ.
urinary excretion: ¡50-300 mg/d
Á¤»ó ¹Ì±¹¼ºÀÎÀÇ ÇÏ·ç Ca¼·Ãë·®Àº 600-800 mgÀε¥ ÀÌÁß ¹ÝÀÌ Èí¼öµÇ¸ç
osteoporosis¸¦ ¿¹¹æÇϱâ À§ÇÑ ÇÏ·ç Çʿ䷮Àº 800-1500 mgÀÌ´Ù.
Fig 340-3 calcium homeostasis
Intestine ¢¢ ECF ¢¢ Bone
(500-1500) ¡¡ (900-1400)
kidney
(150-300)
4. Vitamin D
7-dehydrocholesterol --> previtamin D3 --> vit D3 --> 25(OH)vit D3 --> 1,25(OH)2D3
(UVB) (liver) (kidney)
* ÀÛ¿ë
intestine¿¡¼ Ca, P Èí¼ö Áõ°¡
bone¿¡¼ Ca Èí¼ö Áõ°¡(resorption¡è) <- osteoclast¼ö¸¦ Áõ°¡½ÃÅ´À¸·Î½á
Parathyroid¿¡¼ PTH ¾ïÁ¦
ÃÖÁ¾ÀûÀ¸·Î Ç÷Áß Ca, P ³óµµ¸¦ Áõ°¡½ÃÅ´