Muscle Physiology

1
Muscle Physiology
Theme most fish muscle functions anaerobically
swimming fish need more oxygen and suffer from
lactate acidosis- - but they can compensate (Link
this lecture with Jobling Sections 8.5, 8.6. 8.7)
2
Fish Muscle Physiology

• Theme Most fish muscle functions anaerobically
  therefore, fish are in danger of rapid buildup of
  lactic acid from strenuous activity, but they can
  compensate

• Brief review of General Biology (students do this
  on own)
• Review of cellular respiration
• exception - carp can ferment glucose in red
  muscle to form ATP (Comp. Biochem Phys
  51B235-241)

3
Review

• Review of energy
• phosphocreatine (Jobling and basic biology) -
  nitrogenous complex energy for muscle
  function creatine phosphate broken by
  c-kinase / \ to
  urine to ATP
• glucose, c-c-c-c-c-c, soluble in plasma
• glycolysis -oxidation of carbohydrate to pyruvic
  acid
• anaerobic fermentation (in plants -alcoholic
  fermentation)
• aerobic respiration pyruvic acid oxidized, the
  hydrogen removed is picked up by DPN and
  transported to cytochrome system where it is
  passed from one acceptor substance to the next,
  down an energy gradient until is combined with
  OXYGEN to form water.NOTE rotenone and
  antimycin act here
• hemoconcentration - blood more concentrated
  because water has left plasma to move to tissues
  to buffer, RBC's kicked out from spleen (Jobling)
• acidosis - decreased pH in blood, cells, tissues
• hyperglycemia - high blood sugar or glycogen
  (stress related, not mort.(TAF762)
• Glycogen - Jobling covers this storage
  carbohydrate

4
Lactate

• WHERE AND WHEN DOES LACTATE ENTER?
• Case history Forced swimming in catfish
  Caillouet 1967 min lactate 0
  2.8 1 5.4 2 18.0
  5 21.0 10 52.1 15
  59.0 exhaustion (no deaths)

5
Hyperactivity a lethal factor?

• Many authors have shown that when lactate levels
  get too high, the fish will die. For example
  steelhead, cutthroat, rainbow, Atl. salmon, brook
  trout, lake trout, Pac. Salmon, tuna, skipjack,
  haddock. Apparently there is a threshold level
  or danger zone for lactate level in fish. These
  have been suggested for 3 species...
• Coho 125mg
• Haddock 100 mg
• Channel cat 78 mg

6
Lactate and Swimming Mode

• 1) BURST - use of muscle stores of
  phosphocreatine, conversion quick (2 min), no
  chance to mobilize liver stores, no chance for
  intake, temperature independent swimming rapid
  elevation of lactate2) SUSTAINED SWIMMING - use
  equals intake, balance between supply and demand,
  little lactate buildup
• 3) PROLONGED - glycogen use greater than intake
• liver supply used, temperature dependent
• white muscle recruitment late, little lactate
  buildup until then, fatigue from inability to
  supply
• Lactate found after 90 of critical velocity
  (FRBC 33173-176)
• no increase in blood lactate at swimming up to
  93 of the critical velocity, beyond 93, lactate
  increased indicating little white muscle
  recruitment during most swimming
• lactate produced in red muscle is being oxidized
  because plenty of vascularization and aerobic
  metabolism taking place during exercise, red
  muscle contained 2.6x more blood than white
  muscle
• MC p 26-27 staging the white fibers and pink
  fibers are recruited for swimming at sub-burst
  velocities, some species conform to the classic
  90 model (herring, striped bass), some stage the
  entry of white muscle, or bring it in stages
  (carp, rbt).

7
Fish culture/Capture Applications

• Examples of practices causing lactate and
  amounts
• 1) Collection
• A) shocking catfish shocked and held in tubs 2
  days Lactate 49-79 mg (no deaths)
• B) hoop netting and transported 25 min, weighed,
  measured, held 2 days Results -
• normal appearing fish had Lactate 39 -112
• Fish with noequilibrium had Lactate 66 -138
  moribund had lactate 157 -285mg

8
Applications

• 2) Stocking stress Disturbance of acid base
  balance due to accumulation of lactic acid in the
  blood stream is principle cause of delayed
  mortality in planted hatchery trout. J21917,
  CFCult. 1820
• Example competition between resident wild
  trout and hatchery trout AFTER stocking caused an
  increase in blood lactate,resulting in death of
  weaker fish. T8l35, 83120, J1527, 16321,
  19127
• survival after stocking depends on resident
  population J1527, higher lactate levels in
  stocked fish when stocked on a resident pop
  compared to stocking in water with no fish
• Example delayed mortality of 40 at 4 -8 hr
  (4746), survivors had transitory
  hemoconcentration (water to tissues) and acidosis
  while dying fish had more severe acidosis, but
  levels not excessively high and intracellular
  acidosis might be the cause

9
Cumulative Effects

• RESULT -- A COMPLEX OF PHYSIOLOGICAL PROBLEMS
  that the fish must overcome, the complex can lead
  to death. IN THE COMPLEX OF EFFECTS ARE 5 things
• 1. Reduced swimming ability (jfrbc 211183)
  exhausted fish (sockeye) were unable to perform
  at burst speed swimming until 3 hours elapsed,
  even though blood parameters not back to normal
  in exhausted fish.
• 2. Causes Muscle stiffening - physiological
  contracture a form of continued muscular
  contraction that can be brought on by extreme
  muscular fatigue seems biochemically similar to
  rigor mortis. JFRBC18321
• 3. Lactate slows heart - circulation slows,
  compounded by what? poor vascularization of white
  muscle and slow, slow removal. Hemoconcentration
  - plasma fluids delivered to tissues to act as a
  buffer

10
Bohr effect

• 4. Acidosis - lower blood pH
• 5. Lactate effects ability to take up oxygen
• INDIRECTLY BY ACTING ON HEMOGLOBIN -THE BOHR
  EFFECT
• Bohr effect - oxygen affinity curve shifted to
  the right, this causes hemoglobin to have
  affinity for O2 in water

11
Oxygen Dissociation Curve

• Oxygen Dissociation Curve (Jobling calls Hb
  saturation curve - p 128-130) showing
• 1) pH effect (above)
• 2) species effect (right)

12
Fish Recovery from Exercise

• Lactate removal takes time
• To repay oxygen debt for fatigue, must deep
  ventilate for 3 hr before being able to perform
  burst level
• slow heart, poor circulation PLUS lactate
  molecule diffuses slowly through fish tissues
  (TAF 98266), y axis below is lactate level
  (mg), x axis is time, lines for 3 species of fish

13
LDH

• Role of LDH The enzyme LDH which mediates
  lactate to pyruvate interconversion has been
  studied extensively in fish, particularly about
  physiological significance of different isozymes
• After conversion to pyruvate, the carbon skeleton
  of lactate may follow various metabolic routes
• l. serve for biosynthesis of glucose and
  glycogen energy storage as a sugar
• 2. serve for biosynthesis of lipids energy
  storage as a fat
• 3. undergo various degrees of oxidation to CO2
  this option elected during and immediately after
  exercise
• 4. carp ferment glucose to L-alanine and
  succinate in red muscle to form an extra ATP
  (Comp. Biochem. Phys. 51B235-241) FERMENTED FISH
  - drunk carp
• WHERE DOES THIS TAKE PLACE???? J291467 and CJZ
  601131 are short, good, clear papers on
  anaerobic exercise in fish and oxidation of
  lactate to CO2, use as "capstone" reading
• Oxidative decarboxylation of first carbon in
  LIVER (highest activity -liver, kid, gills, red
  muscle, heart, w. muscle).
• Diverted to biosynthetic pathways to pyruvate
  and then oxidation in Krebs - most in gill, kid,
  r. musc. liver?????, heart, w.musc.

14

• Conclusions
• Liver plays important role in catabolism of
  lactate
• Gills have chloride cells rich in mitochondria,
  powerhouse to complete oxidation of remaining Cs
• Red muscle and heart have ability to oxidize
  lactate formed in the white muscle
• White muscle has poor ability since most energy
  in white muscle is supplied by anaerobic
  glycolysis.
• Review electrophoresis
• If an enzyme has several phenotypes, it is made
  up of proteins that have different mobilities in
  an electric field because of their charge and
  size. They separate in a gel medium, and can be
  fixed and stained for viewing as a series of
  bands.
• BERRY'S LDH STUDIES (PFC 4513)__________________
  _____________________________homozygote slow
  heterozygote homozygote fast
  
  
  
  
  
  
  _______________________________________
  ________

15
LDH Isozyme Study

• Isozyme, isoenzyme, or allozyme one of a group
  of enzymes that are very similar in catalytic
  properties but may be differentiated by
  variations in physical properties, such as
  isoelectric point or electrophoretic mobility.
  Best known case is lactic acid dehydrogenase.
• This slow isozyme removes lactate 3x faster. It
  is higher in long migrant steelhead, higher in
  headwater rbt pops., and means superior swimming
  stamina in rbt.
• The Study (stock 3608 fish, return 146 for liver
  analysis) Homo-slow
  Hetero Homo-fast
• stocked 876 445
  2287
• expected 18 9
  46
• observed 23 13
  37
• CONCLUSION - no difference in isozyme phenotype
  return so the culturist should breed for
  heterozygosity in population rather than maximize
  a single isozyme