Osmoregulation Chapter 26 & 27

Transcription

1 31 st Lecture Fri 03 April 2009 Vertebrate Physiology ECOL 437 (MCB/VetSci 437) Univ. of Arizona, spring 2009 Kevin Bonine & Kevin Oh Housekeeping, Wed 01 April 2009 Readings Today, Mon 30 Mar: Ch 26 (Ionic and Osmotic Balance ) Wed 01 April: Ch 27 () LAB: Circulation; Lillywhite Fri 03 April: Ch 27 () Chapter 26 & 27 Fri 13 Feb = Exam 1 Lab discussion leaders: 01 Apr 1pm Fred, Jarrett 3pm?? Lab discussion leaders: 08 Apr 1pm xx 3pm xx Research Proposal Meetings 1 2 Galapagos Marine Ecology (ECOL 496O/596O) Summer Session II: July 7-Aug 1, 2009 Spend one month this summer in the Galapagos Islands, Ecuador! Visit seven of the most spectacular islands in the archipelago Vertebrate Do a service project with children at a local school and the Galapagos National Park Do a field ecology project and learn about Galapagos ecology and evolution Earn 3-6 units of graduate or undergraduate credit For more information: Katrina Mangin, mangin@ .arizona.edu, Ionic and Osmotic Balance -Kidney Function -life arose in salty sea -extracellular fluids ~ similar -dist n limited by temperature and osmotic pressure (dehydration, ionic composition) 5 -terrestrial organisms (and their descendents) regulate internal environment (homeostasis) -salt and water regulation (waste excretion) -kidneys, salt glands, gills 6 1

2 Obligatory Osmotic Exchanges 1-Gradients -Frog in freshwater -Fish in ocean 2-Surface-to-Volume Ratio -Small animals dehydrate or hydrate more rapidly -Skin, and Respiratory surface (higher metabolism with higher per/gram respiratory surface) 3-Integument Permeability -Transcellular or Paracellular -Aquaporins = water channel proteins Obligatory Osmotic Exchanges 4-Feeding, Metabolism, Excretion -metabolic waste products ammonia, urea, etc. -metabolic water (desert!) -ingestion of salts -kidneys, salt glands, gills (more later) 5-Respiration -internalize respiratory surface -temporal countercurrent system (dry and cool IN, becomes moist and warm; recover) (countercurrent blood flow also) -temperature regulation vs. water conservation -ectotherm vs. endotherm (in deserts) -Frogs vs. Lizards, Pelvic Patch etc Water Breathing 1. Fresh Blood osmolarity mosm/l Water ~ 50 mosm/l Ambystoma tigrinum -Water Breathing 2. Salt (~1,000 mosm/l) Most marine vertebrates hypo-osmotic (e.g., teleost or bony fishes) - hyperosmotic animals, danger of swelling, losing salts - get their water across skin - dilute urine - active uptake of salts across epithelium - fish gills, frog skin, etc. -danger of losing water, gaining too many salts -drink saltwater - excess salts actively secreted (gills, kidneys) - chloride cells for salt secretion Air Breathing Have to lose water to allow gas exchange - Marine reptiles and marine birds can drink seawater and secrete salts in high [ ] - SALT GLANDS - Mammals rely on kidney (14-8) Water Sources: 1 Free 2 Preformed 3 Metabolic C 6 H 12 O 6 + 6O 2 6CO 2 + 6H

3 Hill et al. 2004, Fig Allometry (16-7) Mouse-to-Elephant Curve 4g shrew eats 2g/day elephant is 1 million x larger Allometry Camel K-rat Lab rats K-rat Oryx Hopping Mouse ORGANS THAT CONTRIBUTE TO OSMOREGULATION IN VERTEBRATES Group Fish Amphibians Reptiles Birds Mammals Osmoregulatory Organs Gills Bladder Intestine Gills Bladder Skin Intestine Intestine Intestines 17 -Air Breathing Desert Mammals Behavior and Physiology Kangaroo Rat -Reduce Activity -Remain in Cool Burrow -Humid -Water into dry seeds -Highly concentrated urine -Very dry feces (rectal absorption) -Metabolic water (Eckert 14-9) 18 3

4 Water Phyllomedusa Lose water: evaporation urine feces salt glands eyes Eleutherodactylus coqui Pough et al., 2001 Phyllomedusa sauvagi Alter behavior and physiology to minimize water loss Water balance limits activity in time and space Amphibs lose most water via evaporation - cutaneous resistance 1 dried mucus 2 cocoon 3 wax Role of microhabitat 19 Pough et al., Water Less evap. Chuckwalla (lizards have more lipids in skin) Monkey Tree Frog Anolis lizard osmoregulation mechanisms in gills, salt glands, and kidneys Alligator Softshell Turtle More evap. Bufo, Spadefoots, Rana Pough et al., 2001 (free water surface) Ionic & Osmotic Homeostasis Salt Secretion: recycle extracellular active intracellular Down electrochemical gradient (Paracellular) 23 (Eckert 14-14) 24 4

5 Figure in Box 26.2 Hill et al Shark rectal glands to dispose of excess NaCl -blood hyperosmotic to seawater, but less salt -more urea and TMAO (trimethylamine oxide) -NaCl actively secreted Chloride Cell Shark Rectal (Eckert 14-36) Salt-secreting cells: -Na/K-ATPase pump in basolateral membrane -generates gradient for Na+ by which Na + /2Cl - /K + cotransporter drives up [Cl - ] in cell -Cl - across apical membrane -Na + follows paracellularly down electrochemical gradient (and H 2 O) -apical membrane impermeable to urea and TMAO -therefore iso-osmotic secretion with lots of NaCl (Eckert 14-36) Nasal/orbital salt glands of birds and reptiles -especially species in desert or marine environments. Hypertonic NaCl secretions (2-3x plasma osmolarity) Allows some birds to drink salt water and end up with osmotically free water slightly different in birds and lizards Amblyrhynchus cristatus Fish Gills Chloride cells involved in osmoregulation -(recall lab paper on smolting) -lots of mitochondria to power ATPases -mechanism similar in nasal glands (birds and reptiles), and shark rectal gland (Eckert 14-14) Hill et al. 2004, Fig

6 Freshwater fish: The mechanism basically reversed to allow uptake of salt from water against concentration gradient Sea Freshwater (recall lab paper on smolting) Switch between getting rid of excess salt in seawater and taking up salt in freshwater proton pump to create electrical gradient Na/K-ATPase to generate Na gradient Growth hormone and cortisol for sea (more active chloride cells with more Na/K-ATPase activity) Prolactin for freshwater (Eckert 14-31) Osmoregulatory Mechanisms Apical surface (faces lumen and outside world) Basal surface (faces body and extracellular fluid) - Active movement of ions/salts requires ATP - Movement of water follows movement of ions/salts Gradients established and used to move ions, water active passive (Eckert 14-12) (14-11) 33 Mammalian Kidney 34 6