i Calcium II. a 4 20Ca 40,08 1 g Ca ~ 25 mmol Ca Department of Biochemistry (V.P.), Faculty of Medicine, MU Brno 2009 2 Calcium in the body : the whole calcium 1,0 -1,3 kg body fluids 1 % bones 99 % ECF 0,1 % IST blood plasma 375 mg 2,5 mmol / l ICF 0,99 % Only free ionized calcium is physiologically effective !! 50 % free, ionized Ca (1,25 mmol / l) 32 % Ca binding to albumin (0,8 mmol / l) 8 % Ca binding to globulins (0,2 mmol / l) 10 % Ca in complexes with anions (0,25 mmol / l) 1 hydrogencarbonates, 3 lactate, phosphate, ... Apatit/e i Ca3(PO4)2 Ca3(PO4)2 Ca2+ Ca3(PO4)2 Ca10P6O242+ 4 Carbonatapatite, hydroxyapatite : Ca3(P04)2 Ca3(PO4)2 Ca2+ Ca3(P04)2 CO32-2 OH-▼ hydroxyapatite is the main structural component of bone ~ 65 % of bone weight 5 Fluoroapatit/e r Ca3(PO4)2 Ca3(P04)2 Ca2+ 2 F- Ca3(P04)2 (dentin/e) ó Insoluble calcium salts : CaCO, - Ca(HC03)2 is „soluble" J it exists in water solution only ! Ca(COO) CaS04 (only slightly soluble - it produces the permanent hardness of water) Ca3(PO4): CaHP04 - Ca(H2PO4)2 is soluble 7 Occurrence and movement of calcium in the body : Daily intake approximately 25 - 30 mmol (phosphate, oxalate, phytate) absorption up to 15 mmol / d secretion up to 7 mmol / d 17 -25 mmol /d Mineral deposit 25 mol Ca (rapidly exchangeable 100 mmol) remodeling of bone 7,5 mmol / d rapid exchange 500 mmol / d ECF 2,5 mmol / l total 35 mmol only ICF signal function 0,1 Mmol / l filtration 240 mmol / d I / H X tubular resorption 230 mmol / d Excretion fraction max. 5 % PTH decreases it, calcitonin and high supply ises it 5 - 6 mmol /d 8 Calcium homeostasis : 1/ parathyrin (PTH, parathyroid hormone) 2 / calcitonin (thyreocalcitonin) 3 / calcitriol 4 / (osteocalcin) 9 Parathyrin (PTH) (1) : prepro-PTH 115 AA pro-PTH 90 AA PTH 84 AA t1/2 ~ 3 - 5 min N-terminal sequence (28 AA) ® biological activity hypocalcemia ® incr. of PTH hypercalcemia, calcitriol ® decr. of PTH incr. = increase/d decr. = decrease/d 10 Parathyrin (PTH) (2): membrane receptor (bone, kidney) 1 adenylatcyclase 1 i incr. intracellular cAMP 1 incr. intracellular calcium 1 i phosphorylation of protein by kinases activation of enzymes/proteins with end biological effect of hormone 11 Sensor for calcemia : receptor ® Gq- protein ® incr. in P-Ca2+ has hier inhibition influence (the difference from other cells !!) sensor in parathyroid gland 12 Effect of PTH : 1/ bone: ® osteoclast ® bone resorption ® incr. calcemia 2/ kidney: • incr. resorption of Ca2+ ® incr. calcemia, decr. calciuria • decr. resorption of HPO42- ® incr. phosphate- uria • incr. 1a-hydroxylation of calcidiol (prox. tubulus) ® calcitriol ® incr. gut resorption 3/ gut: incr. intestinal resorption (calcitriol) ® incr. calcemia 13 Calcitonin : (thyreocalcitonin, 32 AA) • antagonist of PTH, effect stimulated by estrogens • limited signification for regulation, protection against violent incr. of calcemia • calcemia is in control of the calcitonin secretion (sensor similar to parathyroid gland) • decr. bone resorption, incr. new production of matrix (treatment of osteoporosis) • decr. reabsorption of Ca and phosphate in the kidney tubule ® incr. exkretion of Ca and phosphate • it is species-specific (salmon calcitonin has 50 % of AA identical with the human one) • analgesic effect in bone pain 14 Calciols : 7-dehydrocholesterol (liver) calciol (skin uv ) calcidiol (liver 25oc-Oh) ® the main metabolite of calciol in plasma ( < 10 mmol / l, season differences, t1/2 ~ 20-30 d, bonding to D-binding protein) calcitriol (kidney i<*oh) inhibition: incr. calcitriol incr. calcitonin excess in intake of Ca stimulation: PTH at hypocalcemii somatotropin Calcitriol : 1/ enterocyte: incr. resorption of Ca into ECF - mechanismus: • change of conformation of cytosol calmodulin ® more effective bonding of Ca2+ ® ® easier Ca2+ crossing of the membrane • calbindin (= CaBP = calcium binding protein) induction of its synthesis ® possibility of Ca transport in the cell • Ca2+-ATPase, ® induction of its synthesis ® draw Ca from enterocyte to ECF 2/ bone: regulation of resorption and new formation of bone tissue = the opposite actions, the mechanismus not understandable 16 Osteocalcin (1) : = BGP = bone Gla protein 49 AA t1/2 ~ 4 - 5 min • contents 3 carboxyglutamate (Gla) for the bond of Ca2+ see next • regulates the deposit of bone mineral • marker of bone remodeling (osteoblast activity in forming of organic matrix) 17 Osteocalcin (2) i C carboxylation of Glu T C 2 C 2 — (vitamin K) f 0 í2 C g-carboxyglutamic acid (Gla) C /u\ C -C H -C X XN - ( C C ■ i ( ( H (b á + bonding of Ca2+ c —C i -C / y 0 n u C 2 0 C -C ' x N - 1S Calcium (1) : • in the Czech Republic suffers from osteoporosis every 3rd woman and every 5th man • needed calcium - 1 g / d (-25 mmol / d) older man + woman in menopause - 1,5 g Ca / d • »Y g Ca - Y l milk - 65 g solid cheese - % l white yogurt 19 Calcium (2) : in childhood and during adolescence we utilize ~ 50 % from given Ca in adulthood we utilize ~ 20 - 25 % from given Ca !! Ca is absorbed at most - from medium-fat dairy products - from some vegetable (cauliflower, Brussel sprout, chicory, broccoli) - from sour dairy products (sour milk, yogurt, ....) more Ca is absorbed from the acidic products than from milk alone !! - from marginal sources: poppy seed, walnut, sardines 20 Calcium (3) : • unsuitable sources of calcium - spinach - high content of oxalates ® formation of insoluble Ca(COO)2 - processed cheese - fortified with large amount of phosphates ® formation of insoluble Ca3(PO4)2 a CaHPO4 - Coca Cola comprises considerable amount of phosphoric acid !! - foliar vegetable with high content of Mg (magnesium should be taken one half less than calcium) 21 The solution „ACD - R 110" ( preparation of conserved blood, „citrate blood" ) 1 Natrii citras dihydricus ( Na3C6H5O7 • 2 H2O ) 1,4 g Acidum citricum monohydricum ( C6H8O7 • H2O ) 0,5 Glucosum ( C6H12O6 ) 2,5 Aqua pro injectione ad 100,0 pH of the solution » 5,1 ± 0,1 100 ml of the solution + 350 to 450 ml of blood 22 The solution „ACD - R 110" ( preparation of conserved blood, „citrate blood" ) 2 blood (400 ml) + ACD slution (100 ml) ® conserved blood (500 ml) 1,4 g of citrate (Mr = 294,10) / 500 ml ® 2,8 g / l 2,8 / 294,10 = 9,52 mmol / l 0,5 g of citric acid (Mr = 210,14) / 500 ml ® 1 g / l l / 210,14 = 4,75 mmol / l totafcitric anion: 14,28 mmol / l 23 The solution „ACD - R 110" ( preparation of conserved blood. „citrate blood" ) 3 1 conserved blood (500 ml) ® » 7,14 mmol of citrate anion CH2-COO-| Ca2+ 3 Ca2+ + 2 citrate3- ® HO-C-COO- ® Ca3(citrate)2 CH2-COON N Ca2+ ✓ ✓ CH2-COO- Ca3(citrate)2 = calcii citras = calcium citrate is UNDISSOCIATED salt, HO-C-COO-1 Ca2+ 1 ✓ soluble in water 1 CH2-COO- = the exception: undissociated salts are insoluble !! On this exceptional solubility of undissociated salt is based almost the whole blood transfusion service !! In the conserved blood must not be present any undissociated and concurrently insoluble salt, it is precipitate (e.g. calcium oxalate) ! The citrate anion is added in greate abundance (see next), so it bonds (removes) safely from the solution all calcium ions, needed for blood clotting. 24 The solution „ACD - R 110" ( preparation conserved blood, „citrate blood" ) 4 3 Ca2+ + 2 citrate3" ® Ca3(citrate)2 1,5 Ca2+ + 1 citrate3" 1 mmol of citrate binds cca 1,5 mmol of free Ca 7,14 mmol of citrate (in 500 ml of conserved blood) are able to bind 10,7 mmol of (free) Ca it is {theoretically) Ca from more than 4 l of blood !! P-[tCa] » 2,5 mmol / l At big volumes of transfused blood we should think about origin of possible hypocalcemia ! (® administration of calcii gluconas from the 2nd transfusion ?) 25 ± 26