Calcium regulation.pptx

Good

1. Calcium regulation Presented by: MOHD MONISH M Pharm (Pharmacology) 2 nd semester SPER, JAMIA HAMDARD

2. Presentation outline Calcium Homeostasis…………………………………………………………………….03-04 Calcium regulating hormones…………………………………………………………..05 Parathyroid Hormone……………………………………………………………………..06-09 Vitamin D…………………………………………………………………………………….10-12 Calcitonin…………………………………………………………………………………....13-14 Physiological actions of calcium……………………………………………………….15 References…………………………………………………………………………………..16 2

3. Calcium homeostasis Calcium is an essential element that serves an important role in skeletal mineralization. More than 99% of the calcium in the body is stored in bone as hydroxyapatite, 0.99% in blood and 0.01% inside cells. Normal blood calcium level ranges between  9 - 10.5 mg / dL.  Calcium in the blood exists in three forms: Free- ionized - diffusible, biologically active. Bound to anions-  e.g. phosphate – diffusible, not biologically active. Bound to proteins-  (mainly albumin) – not diffusible, not biologically active. 3

4. Absorption of Calcium Agents Increases absorption Low calcium intake Vitamin D PTH Agents decreases absorption Oxalates, phosphates . Glucocorticoids Phenytoin Facilitated diffusion from entire small intestine Carrier mediated active transport under influence of vitamin D in duodenum. 4

5. CALCIUM REGULATING HORMONES 5

6. Parathyroid Hormone i s a polypeptide hormone that helps to regulate plasma Ca2+ by affecting bone resorption/formation, renal Ca2+ excretion/reabsorption, and calcitriol synthesis. In kidneys, it increases calcium  reabsorption  mainly from distal convoluted tubule, and proximal part of collecting duct, and inhibits phosphate reabsorption in the proximal tubule, increasing its excretion in urine.  PTH also increases the conversion of 25-hydroxycholecalciferol to the  1,25-dihydroxycholecalciferol,  which increases the absorption of calcium ions from the GI tract, indirectly.  PARATHYROID HORMONE (PTH) 6

7. KIDNEY PTH binds to receptors on cells of PCT inhibits sodium phosphate co-transporters decrease sodium phosphate reabsorption thus increase urinary phosphate excretion. PTH binds to receptors on principal cells of DCT sodium/calcium channel upregulation increase calcium reabsorption from urine. 7

8. BONE PTH increases extracellular calcium levels is by stimulating osteoclast formation in bone. 8

9. Intestine PTH increases extracellular calcium levels is by helping convert cholecalciferol into Vit D. It does so by upregulating enzyme 1 α - hydroxylase. 9

10. Vitamin D is a fat-soluble steroid. It includes  Ergocalciferol , which is called as vitamin D2, and  cholecalciferol  known as vitamin D3, derived from pro-vitamin D (7-dehydrocholesterol). Activation of Vitamin D occurs in 2 steps. First:  Cholecalciferol is converted into 25-hydroxycholecalciferol in liver . Second:  25-hydroxycholecalciferol is converted into 1,25-dihydroxycholecalciferol in kidney , by enzyme 1 α- hydroxylase enzyme.  Now, this 1,25-dihydroxycholecalciferol increases the calcium level in plasma. VITAMIN D 10

11. Activation of Vit-D 11

12. Actions of Vitamin D Increase absorption of calcium and phosphate from intestine. Increase reabsorption of calcium and phosphate from bone. Increase tubular reabsorption of calcium and phosphate in kidneys. Cell differentiation: particularly of collagen and skin epithelium. Important for cell mediated immunity and coordination of the immune response. 12

13. Calcitonin  is secreted by the parafollicular cells, often called as C cells, situated amongst the follicles in the butterfly-shaped thyroid gland. Its normal plasma level is 1 to 2 ng/dL. Calcitonin is a hypocalcemic hormone whose actions generally oppose those of PTH. In Kidneys  - Calcitonin inhibits reabsorption of calcium and phosphate from renal tubule and excreting them. On Bones  - Calcitonin inhibits osteoclasts and stimulates osteoblastic activity. Thus, decreasing plasma calcium as a result. CALCITONIN 13

14. Effect on bone Calcitonin binds to calcitonin receptor on basal osteoclast surface – G protein coupled receptor activation – Adenylate cyclase activation – ATP converted to 3’,5’-cAMP – Increase cAMP levels – decrease no. of osteocyte arms formed – decrease bone resorption. 14

15. Physiological Functions of Calcium Controls of Excitability of Nerves and Muscle Maintains integrity of cell membrane and regulates cell adhesion Essential for muscular contraction Blood clotting Formation of bone and teeth Hormonal and neurotransmitter release Second messenger in some hormonal action 15

16. References Osmosis from Elsevier, Calcium and phosphate regulation, n.d. https://www.osmosis.org/notes/Calcium_and_Phosphate_Hormonal_Regulation , accessed 15/04/2023. Thomas D. Nolin and Peter A. Friedman , Agents affecting mineral ion homeostasis and bone turnover , The pharmacological basis of therapeutics, Goodman & Gilman’s, 13 th edn. MC Graw Hill Education: 2018: 887-906. 16

17. THANK YOU 17