Electrogenic proton transport in epithelial membranes

Area of Science:

• Cellular Physiology
• Biophysics
• Renal Physiology

Background:

• Polar epithelial cells possess robust proton transport capabilities.
• The turtle bladder's apical membrane features a proton-translocating ATPase, an electrogenic proton pump.
• This pump tightly couples proton translocation to ATP hydrolysis, functioning as an ideal electrogenic pump.

Purpose of the Study:

• To develop a more detailed model of proton transport across the turtle bladder epithelium.
• To account for previously unexplained experimental results concerning proton pump behavior.
• To better understand the functional characteristics of the electrogenic proton pump.

Main Methods:

• Utilized an intact epithelial preparation of the turtle bladder for in vitro studies.
• Applied principles of equivalent circuit analysis and nonequilibrium thermodynamics.
• Formulated a new working model based on detailed assumptions of transport steps.

Main Results:

• Proton transport rate is nearly linear with the electrochemical potential gradient for protons.
• The developed model explains several unexplained experimental observations.
• The proton pump exhibits characteristics of both an electromotive force and a constant current source, depending on conditions.

Conclusions:

• The new model provides a more comprehensive understanding of proton transport mechanisms in the turtle bladder.
• The electrogenic proton pump's behavior is complex and condition-dependent.
• Further research can build upon this model to explore acid-base regulation in urinary epithelia.