Metabolic pathways coupled to H+ transport in turtle urinary bladder

Area of Science:

• Cellular Physiology
• Metabolic Biochemistry

Background:

• Active proton (H+) transport in the turtle urinary bladder relies on an ATPase.
• Mitochondrial oxidative phosphorylation is the typical ATP source, but alternative pathways may supply the pump.

Purpose of the Study:

• To investigate the specific metabolic pathways supplying ATP for proton transport.
• To understand the coupling between cellular metabolism and H+ pump activity.

Main Methods:

• Studied the correlation between H+ transport rate and oxidation of labeled substrates (glucose, butyrate, oleate, beta-OH-butyrate).
• Assessed the impact of various substrates on H+ transport in depleted turtle bladders.
• Examined the relationship between H+ transport, lactate production, and cellular ATP/ADP levels.

Main Results:

• H+ transport was coupled to the oxidation of glucose, butyrate, oleate, and beta-OH-butyrate.
• Glucose, pyruvate, lactate, acetate, butyrate, and beta-OH-butyrate stimulated H+ transport.
• No coupling was observed between H+ transport and lactate production.
• Decreased H+ transport led to increased epithelial cell ATP and decreased ADP levels.

Conclusions:

• Proton pump ATP supply is derived from carbohydrate and fatty acid oxidation.
• Changes in ATP and ADP levels indicate a link between H+ transport and cellular oxidative metabolism.