Regulation of Acid-Base Balance PDF

Magnesium Total body stores: 24g 99% intracellular Normal magnesium concentration is 1.7-2.6 mg/dL (or 0.7-1.05 mmol/L) Only 70% of serum magnesium is free (the rest is complexed to albumin) Multiple functions due to its role as an enzymatic cofactor Renal Handli...

Magnesium Total body stores: 24g 99% intracellular Normal magnesium concentration is 1.7-2.6 mg/dL (or 0.7-1.05 mmol/L) Only 70% of serum magnesium is free (the rest is complexed to albumin) Multiple functions due to its role as an enzymatic cofactor Renal Handling of Magnesium ▪Kidneys filter 2000-4000 mg/d Filterable component is the free serum magnesium (70% of total level) Different segments of the nephron are tasked with magnesium reabsorption 1. 10-20% proximal convoluted tubule 2. 70% loop of Henle 3. 10% distal convoluted tubule Magnesium and the TAHL Responsible for 40-70% of magnesium reabsorption Paracellular mechanism similar to the calcium 5 vlbr Magnesium and the Distal Convoluted Tubule Responsible for 5-10% of magnesium reabsorption Active transcellular transport Process coupled to potassium and sodium transport Thiazide diuretics which act on the NCC channel, produce hypomagnesemia Factors that alter renal regulation of magnesium Increase magnesium absorption o Dietary restriction o PTH o Glucagon o Calcitonin o Vasopressin o Aldosterone o Amiloride o Metabolic alkalosis o EGF Decrease magnesium o Hypermagnesemia absorption o Metabolic acidosis o Phosphate depletion o Diuretics ▪ (loop and thiazide) o Anionic antimicrobials ▪ (aminoglycosides, amphotericin) o Chemotherapy (cisplatin) o Immunosuppressants ▪ (tacrolimus, cyclosporine) 6 vlbr  Regulation of Acid-Base Balance Acids and bases (definitions and meanings) Molecules containing hydrogen atoms that can release hydrogen ions in a solution are referred to as acids, o Eg (HCI) ionizes in water to form (H+) and (Cl-) ions. o (H2CO3) ionizes to form H+ and (HCO3-) ions Volatile and Non-volatile Acids A base is an ion or a molecule that can accept an H+. Volatile Acids o For example, HCO3- is a base because it H2CO3 formed from H2O + CO₂ by carbonic can combine with H+ to form H2CO3. anhydrase o HPO4- is a base because it can accept an o Dissociates into H+ + HCO3- H+ to form H2PO4- o Produced by oxidative metabolism of CHO & Lipids Mainly in RBC and renal The proteins in the body also function as bases tubular cells because some of the amino acids that make up o Excreted through LUNGS as CO2 gas proteins have net negative charges that readily o H₂CO₃ can be converted back to H₂O accept H+ and CO₂ by the same enzyme thus Alkalosis refers to the excess removal of H+ from called volatile acid the body fluids. Excess addition of H+ is referred to as acidosis. Concept of pH Non-volatile Acids Are generated during catabolism of: o amino acids, o Phospholipids, o nucleic acids Acids that do not leave solution, once produced they remain in body fluids until eliminated by KIDNEYS Are most important fixed acids in the body Other blood acids such as lactic acid, ketone bodies and fatty acids called non-volatile acids Average normal blood pH=7.35-7.45 o Sulfuric acid Extracellular fluid pH= 7.4 o phosphoric acid The pH of urine can range from 4.5 to 8.0, o Organic acids depending on the acid-base status of the The body produces ↑↑ acids than bases extracellular fluid. o Acids take in with foods. Homeostasis of pH is tightly controlled o Cellular metabolism produces CO₂ o 7.45: Alkalosis (alkalemia) lipids and proteins o