Lecture 8: Hypoxia & Metabolism Case Studies PDF

Lecture 8: 22 Jan Hypoxia & Metabolism Case Studies Reading: 620-621, 215-219, 202-203, 737-742 1 1  Differential Hypoxia Tolerance 8.15 2...

Lecture 8: 22 Jan Hypoxia & Metabolism Case Studies Reading: 620-621, 215-219, 202-203, 737-742 1 1  Differential Hypoxia Tolerance 8.15 2 2  Maintaining Metabolic Balance in Hypoxia 3 3  Pigment Quantity: Adaptational 26.7 4 4  spleen “SCUBA tank” Pigment Quantity: Acute trained seals Peter Sheila Hochachka Thornton 5 5 6 6  Metabolism & O2 demand aerobic dive limit (ADL): how long O2 stores can support resting metabolic rate 26.7 7 7  Diving in Nature 8 8  ADL & Metabolic Rate ADL based on resting metabolic rate what else are diving seals doing? how do they keep O2 demand low? 1. intermittent locomotion… 2. allow Tb to fall 3. postpone digestion 4. selective vasocon- striction 9 9  Hypoxia & Cells cellular O2 sensing: perhaps membrane-bound heme-containing protein? prolyl hydroxylase? hypoxia inducible factor-1: HIF-1 transcribed and translated at the same rate under all conditions normoxia: prolyl hydroxylase identifies HIF-1 for ubiquitin degradation O2 substrate for prolyl hydroxylase; what happens in hypoxia? 10 10  HIF-1: Hypoxia Box 23.1 (sorta) 11 11  hypoxia responsive element 12 12  Pigment Quantity: Acclimation Hct? Hb? RBC? MCV: mean cell volume HCH: mean cell Hb MCHC: mean cell Hb content 13 13  Model System Chrysemys picta belli air-breathing limited buccal gas exchange no access to air several months/year 14 14  Cellular Metabolism & Hypoxia Na+/K+ ATPase: 30% of cell O2 consumption Ca2+ pumping as well protein synthesis: 12% 15 15  Suppressing Na+/K+ ATPase activity normoxic K+ pumped anoxic 16 16  Hypoxia: Metabolic Strategies Adjust anaerobic ATP production anaerobic can produce ATP in the absence of O2 but…inefficient & net H+ production consequences? 1. run out of substrate (fuel) low ATP/mol substrate 2. acidify body fluids 17 17  Hypoxia: Anaerobic Strategies 1. run out of fuel Species Liver Glycogen Trout 235 strategy? Sunfish 185 Rat 210 Mouse 220 Goldfish 1300 Turtle 860 hypoxia sensitive vs. tolerant 18 18 Anaerobic Glycolysis ATP/glucose? ox/phos? typical anaerobic fermentation lactate: most vertebrates ethanol: yeast, goldfish ____opine: molluscs 19 19  Increase Anaerobic Efficiency oxidation to succinate or proprionate can increase ATP/glucose 2 or 3-fold 2 ATP Mytilus edulis 4 ATP 6 ATP 20 20  Avoiding acidification fermentation to ethanol e.g. several inverts, goldfish, carp ethanol, CO2 excreted, controlling pH energetic consequences? CO2 + + CO2 CO2 + 8.17 21 21  Avoiding acidification increase tissue (intracellular) buffering capacity: e.g.? mobilize other buffers: turtle carapace 22 22