HNF 462 1st Edition Lecture 15Outline of Last LectureI. Absorptiona. Transporter Mediatedb. Paracellular DiffusionII. BioavailabilityIII. Transport and ExcretionIV. Calcium Concentration Regulationa. PTHb. Calcitriolc. CalcitoninV. Calcium and BoneOutline of Current LectureI. HypocalcemiaII. HypercalcemiaIII. Intracellular Calcium RegulationIV. Neuron SignalingV. Food Components that Affect Calcium BalanceVI. Phosphorus as a Building BlockVII. DigestionVIII. AbsorptionIX. Transport in BloodX. ExcretionXI. Regulation of PhosphorusXII. MagnesiumXIII. Transport and Excretion of MagnesiumXIV. Concentration of MagnesiumThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.XV. Regulation of MagnesiumXVI. Magnesium and PTHCurrent Lecture: Calcium (Cont.), Potassium, and Magnesium1. Hypocalcemia: low calcium concentration in seruma. Most often caused by hypoparathyroidism, and can also be caused by an autoimmune diseaseb. Vitamin D deficiency has important relevance in long term maintenance of 2. Hypercalcemia: high calcium concentration in seruma. Most commonly caused by hyperthyroidism (by tumors), also can be caused by excessive calcium intake in a short timeb. Can cause a buildup of calcium phosphate in organs3. Intracellular Calcium Regulationa. Pumped through cell membrane via diffusion or active transportb. Calcium channels move calcium from the cytoplasm and store it in the mitochondria and endoplasmic reticulumc. Calcium binds to calcium binding proteins, which lowers the calcium levels in the cell4. Neuron Signalinga. Stimulation to neuron axon caused sodium influx into axon = depolarizationb. Depolarization continues to end of axon, where calcium channel opens to allow calcium to enter the fiberc. Calcium influx releases transmitter to the next neuron5. Food Components that Affect Calcium Balancea. Enhance absorption: Vitamin D, sugars/sugar alcohols, and proteinb. Inhibit absorption: fiber, phytic/oxalic acids, excessive Zn/Mg, and unabsorbed fatty acidsc. Enhance Excretion: sodium6. Phosphorus as a Building Blocka. Major component in boneb. Forms salt with calcium in the bone c. DNA/RNAd. ATPe. Creatine Phosphatef. Cyclic AMPg. Phospholipids7. Digestiona. Organic forms are hydrolyzed to inorganic form8. Absorptiona. Passive diffusion or active transportb. Enhancers: Vitamin Dc. Inhibitors: Phytic acid, excessive Mg/Al/Ca9. Transport in Blooda. In free form or bound to hydrogen i. Organic phosphorus (~70%): phosphates, phospholipidsii. Inorganic phosphorus (~30%): HP042- ßàH2PO4-b. Part of phospholipids in the blood10. Excretion mostly via urine11. Regulation of Phosphorusa. Extracellular Regulation: ~70% organic P in the serumb. Intestinal PO4 Absorption: increased by calcitriol, inhibited by calcitoninc. Mobilization from Bone: stimulated by PTH and calcitriold. Renal PO4 Reabsorption: decreased by PTH, increased by calcitriol12. Magnesiuma. Important in bone healthb. Associated with nucleic acids and proteinsc. Stabilizes ATP: low Mg will cause energy metabolism problems because there won’t be enough Mg to bind to ATP, and ATP won’t stabilize13. Transport and Excretion of Magnesiuma. Similar transport to calcium: ~55% is free form in serum, ~30% is bound to proteins in serumi. Calcium will decrease Mg absorption because they compete for the same transporterii. Paracellular diffusion with high concentrationsiii. ATP enzyme that expels Mg outside of the cell into the bloodb. Excreted via urine14. Concentration of Magnesiuma. Small portion of Mg is in the serum; PTH increases [Mg] in serumb. Lower concentration inside the cell than outside the celli. Bound to ATP and nucleic acids inside the cellii. 60% of Mg in the cell is located in mitochondria15. Regulation of Magnesiuma. Intestinal Absorption: Increased with pharmacological concentrations of calcitriolb. Serum Mg is regulated by the kidney (excess will be excreted through urine)c. Renal Reabsorption: i. Increased by PTHii. Decreased by high levels of Mgiii. Decreased by increased blood volumeiv. Decreased by protein/alcohol/caffeine (caffeine decreases calcium reabsorption in the kidneys)16. Magnesium and PTHa. Low Mg = PTH releaseà renal absorption of Mg and Mg released from boneb. Very low Mg with reduce PTH secretionà