Salt and Mineral Absorption PDF

These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or Wo...

These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine. Salt and Mineral Absorption Aaron Marshall, Ph.D. Department of Medical Education  These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine. Session Objectives Review the features of intestinal epithelial cells that promote vectorial transepithelial transport.​ Discuss the role of fluid transport in the GI tract in health and disease.​ Describe the mechanisms of epithelial transport of the GI tract that lead to efficient assimilation of ingested electrolytes (esp. sodium,) and the two minerals calcium and iron​ Distinguish among the regions of the GI tract with respect to their absorptive tasks and mechanisms.​ Discuss the mechanisms regulating calcium and iron absorption, the regulation of these processes, and the clinical outcomes when there is incorrect intake of these minerals Describe the mechanisms of epithelial transport of the GI tract of water-soluble vitamins  These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine. Directional Influences ELECTROLYTE (AND H20) ABSORPTION  These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine. Absorption and secretion of electrolytes and water by SI and colon have a similar setup Secretion occurs in the crypts (of either SI or colon) & Absorption occurs at the surface Both involve transcellular electrolyte flux – Absorptive Mechanisms refer to the active movement of sodium – Secretory Mechanisms refer to the movement of chloride ions.  These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine. Osmotic water flow 290 paracellular route between cells 285 295 transcellular route through cells 290 Salt and solute transport is the driving force for passive water flux by either route 1. Absorption of solutes moves osmolytes into cells and tissue 2. Water flows into hyperosmotic environments (too much salt/solute)  These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to Transcellular Transport University of Cincinnati, College of Medicine. mechanisms Epithelial cells express subsets of these transport proteins to produce net movement of ions and solutes across the epithelial layer Absorptive Secretory Sodium-coupled nutrient Chloride secretion absorption – SI and colon – SI only – Also discuss regulation of Cl- Electroneutral NaCl secretion absorption Bicarbonate secretion – SI and colon Electrogenic sodium – Duodenum only absorption – Colon only Sodium-coupled bile acid absorption – Ileum only Not detailed on subsequent slides  These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine. Sodium absorption in the intestine Glucose-galactose malabsorption Sodium-coupled nutrient absorption exemplified by the uptake of glucose from the intestinal lumen. SGLT1, sodium–glucose cotransporter 1. These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine.  These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine. NaCl absorption in the small intestine and colon Electroneutral absorption of NaCl enters across the apical membrane via the coupled activity of a sodium/hydrogen exchanger (NHE) and a chloride/bicarbonate exchanger (DRA). The route of basolateral chloride exit via the potassium/2 chloride cotransporter (KCC1) remains speculative.  These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine. Sodium absorption in the colon +++++ ENaC is aldosterone regulated Electrogenic sodium absorption in the colon. Sodium enters the epithelial cells via epithelial sodium channels (ENaC) and potassium is lost in stool (leaves apical membrane).  These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine. Chloride secretion in the small intestine and colon Chloride uptake occurs via the sodium/potassium/2 chloride cotransporter, NKCC1. Potassium is recycled basolaterally via SK1/KCNQ1 potassium channels. Chloride exit is predominantly via the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine.  These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine. Regulation of Chloride secretion in the small intestine and colon Regulation of chloride secretion by cAMP-dependent agonists such as vasoactive intestinal polypeptide (VIP) and prostaglandins. These agonists activate adenylyl cyclase (A.C.) via a stimulatory G protein (Gs) leading to an increase in intracellular cAMP. This in turn activates the cAMP-dependent protein kinase (protein kinase A), causing the insertion of NKCC1 cotransporter molecules into the basolateral membrane and opening of CFTR (via phosphorylation).  These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine. Water handling along the GI tract Absorption 7.5 L 1.4 L 1.5 L Stomach Small intestine Colon 0.1 L Dietary excreted intake 1.0 2.0 1.0 saliva pancreas bile 2.5 1.0 intestinal secretion gastric Secretion  These PPT slides are intended for private use for University of Cincinnati, College of Medicine students ONLY. Do NOT distribute or transmit them in any form by any mechanical, photographic or electronic process, including electronically or digitally on the Internet or World Wide Web or to any persons not matriculated to University of Cincinnati, College of Medicine. Diarrheal diseases Givens: Healthy small intestine’s absorptive capacity is ~9 L Healthy colon’s absorptive capacity is ~4.5 L Small Intestinal Colonic Health Disease (reduced Disease absorptive capacity) (reduced absorptive capacity