Circulation 8 Flashcards
carbonic anhydrase (2)
- essential enzyme for many different systems/processes
- found in almost all living things
CA reaction
- catalyzes CO2 + H2O <–> H+ + HCO3-
what is CA’s role in respiratory gas exchange in the RBC (2)
- CO2 excretion in RBCs
- converts CO2 into H+ and HCO3- at tissues and converts these back into CO2 at the gills
what is unique about sharks and CO2 excretion (2)
- sharks don’t need their blood
to maintain normal CO2 excretion - hagfish and chondrichthyans have CA outside the RBC at the gills
what is CA’s role in respiratory gas exchange (2)
- facilitates CO2 excretion in gills and RBC
- facilitates O2 delivery in the heart and red muscle (aerobically-demanding tissues)
what environmental condition drives O2 offloading (2)
- hemoglobin pH sensitivity/Bohr effect
- O2 saturation (O2 binding affinity) decreases when pH decreases
root effect (2)
- describes how telosts experience a decrease in binding affinity AND binding capacity when pH decreases
- membrane bound CA and root effect help with O2 offloading at tissues
betaNHE (2)
- protects O2 binding at gills
- moves H+ out of Hb in low pH stress to maintain O2 binding at the gill
how do the sequences in fish with gill CA differ from those without
- histidine substitution (his-64) with a different amino acid occurs
how does his-64 contribute to activity (2)
- RBC CA activity is significantly lower in fish with gill CA
- CA activity is driven by His-64
how has the pattern of CA evolved in fish with and without gill CA
- CA isoform types are mutually exclusive; only those without gill CA have high activity RBC CA
why was the red drum used to study CA in teleosts (4)
- has root effect
- has betaNHE
- has membrane-bound CA
- has high-activty RBC CA
does RBC CA activity impact O2 offloading rate
- yes, CA addition increases O2 offloading from baseline and vice versa
how much does CA impact O2 offloading
- CA inhibition decreases O2 offloading 1:1
- CA addition increases O2 offloading 1:1
red blood cell CA: activity (2)
- dictated by amino acid His-64
- may have evolved with O2 delivery capabilities
red blood cell CA: activity in red drum
- dictates Hb-O2 offloading in red drum
what is the role of membrane bound CA
- takes HCO3- from the chloride exchanger and H+ from betaNHE and converts it to CO2 at the tissues
will hypoxia training help fish outcompete non-acclimatized counterparts (3)
- CA4a gene expression, protein levels and localization did not change
- CA4a activity does not change
- no, aerobic performance did not change
standard metabolic rate
- resting swim speed with relatively low O2 consumption
maximum metabolic rate
- highest swim speed until failure with relatively high oxygen consumption
burst during performance
- level when ‘sprinting’ starts
aerobic scope
- O2 consumption and swim speed between standard metabolic rate to maximum metabolic rate
what was the predicted outcome of hypoxia acclimatized fish (2)
- increased aerobic scope
- increased maximum metabolic rate
what were some changes that did occur in hypoxia acclimatized fish (3)
- increased Hb binding affinity
- increased O2 uptake
- decreased Hb pH sensitivity
membrane-bound CA
- CA4a is maintained under hypoxia, but is not as important for performance in the red drum
what is the function of CA4a in zebrafish
- respiratory gas exchange
what is the function of CA4a in rainbow trout
- metabolic processes
what is the function of CA4a in red drum
- acid-base and ion regulation
