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CHAPTER 10 Ion and Water Balance PowerPoint® Lecture Slides prepared by Stephen Gehnrich, Salisbury University Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview Three homeostatic processes Osmotic regulation Osmotic pressure of body fluids Ionic regulation Concentrations of specific ions Nitrogen excretion Excretion of end-products of protein metabolism Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ionic and Osmotic Challenges Marine environments Animals tend to gain salts and lose water Freshwater environments Animals tend to lose salts and gain water Terrestrial environments Animals tend to lose water Many animals move between environments and must be able to alter their homeostatic mechanisms Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ionic Regulation Strategies to meet ionic challenges Ionoconformer Ionoregulator Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Osmotic Regulation Strategies to meet osmotic challenges Osmoconformer Internal and external osmolarity similar For example, marine invertebrates Omoregulator Osmolarity constant regardless of external environment For example, most vertebrates Ability to cope with external salinities Stenohaline Can tolerate only narrow range Euryhaline Can tolerate wide range Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Osmolarity (mol/L): the osmolar concentration of a solution (commonly used in biology Osmolality (mol/kg): the osmolal concentration of a solution Osmotic concentration (Osm) Salinity (%0, ppt, parts per thousand) NaCl 150 mmol Dissolve to Na+ 150 mmol, Cl- 150 mmol Osmolarity = 300 mmol/L Osmotic concentration = 300 mOsm Water 1L NaCl 500 mmol Osmolarity = 1000 mmol/L Osmotic concentration = 1000 mOsm Salinity = 500*58 =29 g/L (ppt) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Osmotic properties of cells extracellular ion concentration = intracellular ion concentation ? Body fluid (extracellular) osmolarity = intracellular osmolarity ? Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Osmoregulation in fishes (cyclostome) (freshwater fishes) (Euryhaline fishes) (seawater fishes) freshwater Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings seawater Ionic and Osmotic Regulation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Table 10.1 4 types of strategies for facing salt and water problems Osmoconformer Ionconformer Osmoconformer Ionregulator Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Osmoregulator Osmoregulator Ionregulator Ionregulator Classification of Solutes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 10.4 Osmoconformers (but not ion-conformer) The cells of osmoconformers are able to cope with high extracellar Osmolarity by increasing their intracellular osmolarity. Organic osmolytes: urea, trimethylamine oxide (TMAO) Elasmobranch: shark, ray hagfish coelacanth Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings crab-eating frog Marine elasmobranch are hyperosmotic but hypoionic to seawater Shark rectal gland Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Most types of FW animals share similar regulatory mechanism Teleost Ray (elasmobranches) Lamprey (cyclostomes) Frog Soft-shell turtle Mussel Crayfish Leech Mosquito larvae Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Strategies of FW fishes: Possessing an integument with a low permeability to salts and water Do not drink water Production of dilute urine Reabsorption of salts from kidney Ingesting salts from food Active absorption of salts from skin (amphibian) or gills (fish) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Osmoregulation in marine animals Marine teleosts Strategies: Possessing an integument with a low permeability to salts and water Drink seawater Production of isotonic urine Excretion of salts from kidney (Mg2+, SO42-) Active secretion of salts from gills (Na+, Cl-) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Air-breathing animals: sea bird, sea turtle, iguanas, Osmoregulatory problems: Dehydration through their respiratory epithelia Strategies: Drink seawater Production of isotonic urine Active secretion of salts from salt glands (Na+, Cl-) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Salt gland in sea birds (nasal gland) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Shark rectal gland Salt gland of Sea turtle Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Salt gland of marine Iguanas Ion- and osmo-regulation of animals: from molecular to cellular function Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Relative permeability of phosolipid bilayer (cell membrane) to molecules and ions Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Mechanisms for trans-membrane movement of ions Diffusion (move down electrochemical gradient) Passive transport (move down electrochemical gradient) Active transport (move against electrochemical gradient) Passive transport: Facilitated Ion channels Carrier proteins diffusion Active transport: Primary active transport Secondary active transport Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 5 types of ion transporters Primary active transport Passive transport secondary active transport Passive transport cotransporter Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings exchanger Passive transport through “passive transporter” Facilitated diffusion Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Primary active transport through Na+/K+-ATPase (Na+ pump) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 3 major types of active transporters: Na pump (Na/K-ATPase) Ca pump (Ca-ATPase) H pump (H-ATPase, V-ATPase) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Secondary active transportrs Na/H exchanger Na/Ca exchanger Na/K/Cl cotransporter Cl/HCO3 exchanger Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Kinetics of various ion transport proteins Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Epithelial Tissue Epithelial tissues form boundary between animal and environment External surfaces For example, skin Internalized surfaces For example, lumen of digestive and excretory systems Epithelial tissues have physiological functions in respiration, digestion, and ion and water regulation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Epithelial Tissue Properties for Ion Movement Four features of transport epithelia Asymmetrical distribution of membrane transporters Solutes selectively transported across membrane Cells interconnected to form impermeable sheet of tissue Little leakage between cells High cell diversity within tissue Abundant mitochondria Large energy (ATP) supply Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Epithelial Tissue Properties for Ion Movement Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 10.8 Solute Movement Epithelial cells use two main routes of transport Transcellular transport Movement through the cell across membranes Paracellular transport Movement between cells “Leaky” vs. “tight” epithelia Types of transporters Na+/K+ATPase Ion channels (Cl–, K+, Na+) Electroneutral cotransporters Electroneutral exchangers Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Transcellular and Paracellular Transport Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 10.9 Measurement of trans-epithelial ion transport Ussing chamber Voltage/ Ion clamp technique (Short Circuit Current Vs = 0) ClTransepithelial potential Vout = 0 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Vin = -30 mV Epithelial Cells in Fish Gills Fish gill lamellae composed of Mitochondria-rich chloride cells Pavement cells Some mitochondria-rich ?? Some mitochondria-poor Transport likely carried out by mitochondria-rich cells Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Salt secretion in marine teleosts Salt-secreting cells (chloride cells) Gill filament Branchial chloride cells in gill filament of marine teleosts lamellae filament Salt-secreting cells present in : rectal gland of shark, sea bird, sea turtle gills of marine teleosts K channel Na/K ATPase Epithelial Cl channel (CFTR) Paracellular pathway Na/K/2Cl cotransporter Leaky junction Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Epithelial Cells in Fish Gills (FW fish) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 10.10 Ion Transport by Fish Gills Direction of ion transport depends on water salinity Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 10.11 Hypothesis of Na, Cl uptake in freshwater fish Gas exchange Ion exchange pH regulation Ammonia excretion Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Renal physiology Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Kidney Vertebrate kidneys have six roles in homeostasis Ion balance Osmotic balance Blood pressure pH balance Excretion of metabolic wastes and toxins Hormone production Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Kidney Structure and Function Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 10.19 The Nephron Functional unit of the kidney Composed of Renal tubule Lined with transport epithelium Various segments with specific transport functions Vasculature Glomerulus Ball of capillaries Surrounded by Bowman’s capsule Capillary beds surrounding renal tubule Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Structure of nephron 15% Glomerulus Renal corpuscle Bowman’s capsule Proximal convoluted tubule Proximal tubule Proximal straight tubule Descending thin limb of Henle’s loop Henle’s loop Ascending thin limb of Henle’s loop Thick ascending limb of Henle’s loop Distal tubule Collecting duct Distal convoluted tubule Cortical collecting duct Medullary collecting duct Renal pelvis Ureter Bladder Urethra Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Urine Production Four processes Filtration Filtrate of blood formed at glomerulus Reabsorption Specific molecules in the filtrate removed Secretion Specific molecules added to the filtrate Excretion Urine is excreted from the body Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Filtration Liquid components of the blood are filtered into Bowman’s capsule Water and small solutes cross glomerular wall Blood cells and large macromolecules are not filtered Glomerular capillaries are very leaky Podocytes with foot processes form filtration structure Mesangial cells control blood pressure and filtration within glomerulus Filtrate flows from Bowman’s capsule into proximal tubule Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Blood pressure in the renal glomerulus Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Net filtration pressure GFR Permeability of bowman’s capsule blood A B C urine blood protein Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings A: endothelium (pores) B: basement membrane C: podocyte (filtration slit) Intrinsic control of GFR: 1. Autoregulation of blood pressure of afferent arteriole 2. Renal blood flow regulated by juxtaglomerular apparatus (macula densa, juxtaglomerular cells) 3. Sympathetic activation causes vasocontriction of afferent arteriole and reduces hydraulic permeability (podocytes) of Bowman’s capsule Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Extrinsic Regulators of GFR Hormones Vasopressin (antidiuretic hormone, ADH) Renin-Angiotensin-Aldosterone (RAA) pathway Atrial natriuretic peptide (ANP) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Reabsorption Primary urine Initial filtrate filtered in Bowman’s capsule that is isosmotic to blood Most water and salt in primary urine reabsorbed using transport proteins and energy Rate of reabsorption limited by number of transporters Renal threshold Concentration of a specific solute that will overwhelm reabsorptive capacity Each zone of the nephron has transporters for specific solutes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Reabsorption of Glucose Glucose is reabsorbed by secondary active transport Reabsorbed molecules taken up by the blood Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 10.23 Renal clearance of substance = Amount of substance in urine Amount of substance filtered Glucose clearance= 0 (100% reabsorption) Inulin clearance=1 (no reabsorption, secretion) GFR (L/h) = Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Inulin in urine (mg/h) Inulin in blood (mg/L) Transport in Tubule Regions Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 10.25 Transport in the Proximal Tubule Most reabsorption of solutes and water takes place in proximal tubule Many solutes reabsorbed by Na+ cotransport Water follows by osmosis Proximal tubule also carries out secretion Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 10.27 Secretion Similar to reabsorption, but in reverse Molecules removed from blood and transported into the filtrate Molecules secreted include K+, NH4+, H+, pharmaceuticals, and water-soluble vitamins Requires transport proteins and energy Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ion and Water Transport in the Loop of Henle Descending limb is permeable to water Water is reabsorbed Volume of primary urine decreases Primary urine becomes more concentrated Ascending limb is impermeable to water Ions are reabsorbed Primary urine becomes dilute Reabsorbed ions accumulate in interstitial fluid An osmotic gradient created in the medulla Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Urine concentration: Henle’s loop Reabsorption of water 70% Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Reabsorption of water 30% (regulatory region) Primary active Na reabsorption Coupling of water reabsorption to Na reabsorption Osmolarity increase water Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Proximal tubule: Na reabsorption Na/glucose cotransporter Na/K/Cl cotransporter Ascending limb of Henle’s loop: Na, reabsorption Na/H exchanger Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Urine concentration: countercurrent multiplier system Renal cortex low Interstitial osmolarity high Renal medulla Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Countercurrent flow of circulation (vasa recta) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Renal Na and water regulation: Control of GFR (short-term) Control of Na reabsorption (long-term) Renin-angiotensin Aldosterone hormones baroreceptor Atrial natriuretic peptide (ANP) Vasopressin Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Renin-angiotensin system and aldosterone Activity of renal sympathetic nerve Intrarenal Baroreceptor (JGA) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Renin-angiotensin system Angiotensin-converting enzyme (ACE) Aldosterone (mineral corticoid) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Atrial natriuretic peptide (ANP) stimulates Na excretion Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Vasopressin Also called antidiuretic hormone (ADH) Peptide hormone Produced in hypothalamus and released by posterior pituitary gland Increases water reabsorption from the collecting duct by increasing number of aquaporins Release stimulated by increasing plasma osmolarity detected by osmoreceptors in the hypothalamus Release is inhibited by increasing blood pressure detected by stretch receptors in atria and baroreceptors in carotid and aortic bodies Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Regulation of water reabsorption Collecting duct Aquaporin (water channel) Vasopressin regulated Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Vasopressin Increases Cell Permeability Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 10.34a Renal (metabolic) acid-base regulation in distal tubule and collecting duct A-type intercalated cell Acid secretion Apical H-ATPase (proton-ATPase) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings B-type intercalated cell Base (bicarbonate) secretion Apical Cl/bicarbonate exchanger (anion exchanger)
