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Diet

Calcium balance. Diet. 1.000 mg. Absorbed 500 mg. Formation 280 mg. Calcium pool. Bone. intestine. reabsorption 280 mg. Secreted 325 mg. Stool. Reabsorbed 9.825 mg. Filtered 10.000 mg. 825 mg. Kidney. Urine. 175 mg. hormones regulating Ca 2+ balance.

vladimir-zimmerman
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Diet

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  1. Calcium balance Diet 1.000 mg Absorbed 500 mg Formation 280 mg Calcium pool Bone intestine reabsorption 280 mg Secreted 325 mg Stool Reabsorbed 9.825 mg Filtered 10.000 mg 825 mg Kidney Urine 175 mg

  2. hormones regulating Ca2+ balance Parathyroid hormone ( = PTH ) produced in parathyroid gland) • increases Ca2+ reabsorption in the kidney Vitamin D ( = 1,25 - Dihydroxycholecalciferol ) generated from Cholecalciferol in the kidney ● increases Ca2+- reabsorption in kidney and intestinum ● deposition of Ca2+ in the newly formed bone Calcitonin ( = Thyreocalcitonin ) from C cells of thyroid gland ● stimulate Ca2+ excretion in the kidney

  3. Skin (+ UV) Liver: Dehydro -Cholesterin Cholecalciferol Kidney: 1,25-(OH)2-Cholecalciferol 25-OH-Cholecalciferol = Vitamin D Genesis of D -hormones Liver:

  4. A: Ca++ Reabsorption 8% 70% 1% 20% II. other influential factors: Alkalosis: increases the reabsorption in distal tubule and acidosis does the opposite 1% Influential factors on Ca++ handling along a Nephron B: Regulation of Ca++-Reabsorption I. hormone: Parathormone: increases overall the Ca++ reabsorption, but strongly in the Henle`s loop and in distal tubule. PTH lowers the reabsorption of NaCl and Water and thus of Ca++ in proximal tubule. The overall result is a net Increase in Ca++reabsorption Calcitonin: inhibits Ca++ reabsorption in Henle`s loop and in distal tubule Calcitriol: increases Ca++ reabsorption in distal tubule increased Plasma phosphate:induces the release of PTH and thus elevates Ca++ reabsorption ECV reduction:increases Ca++ reabsorption and ECV entlargement reduces Ca++ reabsorption

  5. Tubule lumen Interstitial space Ca2+ 3 Na+ 2 Ca2+ Ca2+ 2 Ca2+-sensing receptor lowers levels of cAMP, which otherwise stimulates Na+/K+/Cl- Cotransporter. Arachidonic acid P450 20-HETE Na+ K+ 2 Cl- Ca2+ K+ Ca2+ Receptor Ca2+ Ca2+ Paracellular Diffusion

  6. Chief cell of parathyroid _ _ + + + + + + + + + + PTH _ Ca2+ absorption Ca2+ reabsorption Plasma Ca2+ 8,5-10,6 mg/dl Bone Intestine Tubule Ca2+ reabsorption Kidney Tubule Phosphate reabsorption Conversion of 25-OH-Vitamin D Cu 1,25-(OH)2-Vitamin D

  7. _ _ + + + + + + + + + + _ Chief cell of parathyroid PTH Ca2+ absorption Ca2+ reabsorption Plasma Ca2+ 8,5-10,6 mg/dl Plasma Phosphate Bone Intestine Phosphate Phosphate Tubule Ca2+ reabesorption kidney Tubule Phosphate reabsorption Conversion of 25-OH-Vitamin D to 1,25-(OH)2-Vitamin D

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