Related Experiment Videos
Coupled Na+/H+ exchange in rat parotid basolateral membrane vesicles
1Clinical Investigations and Patient Care Branch, National Institute of Dental Research, Bethesda, Maryland 20892.
The Journal of Membrane Biology
|June 1, 1988
Summary
A pH gradient drives sodium transport in rat parotid glands, suggesting a Na+/H+ antiport. This transporter is amiloride-sensitive and plays a role in salivary fluid secretion.
Area of Science:
- Physiology
- Membrane Transport
- Biochemistry
Background:
- Salivary fluid secretion is crucial for oral health.
- The basolateral membrane of salivary acinar cells plays a key role in ion transport.
- Previous studies suggested a role for ion transporters in salivary secretion, but direct evidence was limited.
Purpose of the Study:
- To investigate the presence and characteristics of sodium transport mechanisms in rat parotid basolateral membrane vesicles.
- To determine if a pH gradient influences sodium transport.
- To identify the specific transporter involved and its potential role in salivary secretion.
Main Methods:
- Utilized highly purified rat parotid basolateral membrane vesicles.
- Performed voltage-clamped experiments to study 22Na uptake under varying pH gradients.
- Assessed the effect of transport inhibitors, including amiloride, furosemide, bumetanide, SITS, and DIDS.
- Investigated the kinetic properties of sodium transport using Michaelis-Menten analysis.
- Examined sodium transport in rabbit parotid basolateral membrane vesicles for comparative analysis.
Main Results:
- An outwardly directed H+ gradient significantly increased 22Na uptake (approximately tenfold) compared to pH equilibrium.
- Over 90% of this pH gradient-dependent sodium flux was inhibited by amiloride (K1 = 1.6 microM).
- Other tested transport inhibitors (furosemide, bumetanide, SITS, DIDS) had no effect.
- Sodium uptake could be driven against a concentration gradient by an outward H+ gradient, indicating active transport.
- Kinetic analysis revealed a single transport system with a Michaelis constant (KM) of 8.0 mM at 23°C.
- Similar pH gradient-dependent, amiloride-sensitive sodium flux was observed in rabbit parotid basolateral membrane vesicles.
Conclusions:
- Provided strong evidence for the existence of a Na+/H+ antiport in rat and rabbit parotid acinar basolateral membranes.
- This Na+/H+ antiport is sensitive to amiloride and is driven by a pH gradient.
- The findings support the hypothesis that this transporter plays a significant role in salivary fluid secretion.