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Correlation between apical intramembrane particles and H+ secretion rates during CO2 stimulation in turtle bladder
Pflugers Archiv : European Journal of Physiology
|January 1, 1986
Summary
Carbon dioxide (CO2) stimulates H+ transport in turtle bladders by increasing rod-shaped intramembrane particles (RSP) in carbonic anhydrase-rich (CA) cells. This suggests RSPs are crucial for active H+ transport.
Area of Science:
- Cell biology
- Physiology
- Biophysics
Background:
- Carbonic anhydrase-rich (CA) cells play a key role in regulating acid-base balance.
- The apical membrane of these cells is involved in proton (H+) transport.
- Rod-shaped intramembrane particles (RSP) are observed in these membranes, but their function is unclear.
Purpose of the Study:
- To investigate the correlation between RSP prevalence in CA cell apical membranes and H+ transport rate.
- To understand the role of RSP in CO2-stimulated H+ transport in the turtle urinary bladder.
Main Methods:
- Morphometric analysis using scanning and freeze-fracture electron microscopy.
- Studied alpha and beta subpopulations of CA cells.
- Correlated apical membrane area and RSP density with H+ transport rates under varying CO2 conditions.
Main Results:
- CO2 exposure more than doubled the apical membrane surface area of alpha cells.
- Apical membrane folding (amplification) increased significantly.
- RSP density increased by approximately 40%, leading to a 5-fold increase in luminal RSPs.
- H+ transport rate increased 9-fold, correlating with RSP recruitment.
Conclusions:
- CO2 stimulation of H+ transport involves the recruitment of RSP to the apical membrane of alpha-type CA cells.
- RSP are associated with active H+ transport and may represent transmembrane components of H+ pumps.