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Amiloride-sensitive Na+ current in the granular duct cells of mouse mandibular glands
Insights
Salivary ducts possess an amiloride-sensitive sodium (Na+) channel on their luminal membrane, distinct from secretory cells. This finding suggests a shared mechanism for sodium handling across different salivary duct types.
Area of Science:
- Physiology
- Ion Transport
- Cell Biology
Background:
- Salivary glands play a crucial role in fluid and electrolyte balance.
- The specific ion transport mechanisms in salivary ducts are not fully elucidated.
- Understanding ion channels in ducts is key to comprehending salivary secretion and reabsorption.
Purpose of the Study:
- To investigate the presence and location of amiloride-sensitive sodium (Na+) conductance in mouse mandibular salivary gland ducts.
- To differentiate ion channel activity between intralobular duct cells and secretory endpiece cells.
- To determine the membrane domain (luminal vs. basolateral) of the identified Na+ conductance.
Main Methods:
- Whole-cell patch clamp electrophysiology on dispersed intralobular duct cells.
- Isolation of basolateral membranes from intralobular ducts for patch clamp analysis.
- Application of amiloride to assess Na+ channel sensitivity.
Main Results:
- A significant amiloride-sensitive, Na+-selective conductance was detected in whole-cell recordings of intralobular duct cells.
- This conductance was absent in secretory endpiece cells.
- Amiloride did not affect membrane conductance in outside-out patches from the basolateral membrane, indicating luminal localization.
Conclusions:
- Evidence supports the presence of a luminal Na+ conductance in intralobular salivary ducts.
- This finding suggests that intralobular ducts actively participate in sodium transport.
- The identified luminal Na+ channel may represent a common mechanism for Na+ handling in both intralobular and extralobular salivary ducts.
Abstract:
Whole-cell patch clamp studies on dispersed cells from the intralobular ducts of mouse mandibular glands reveal the presence of an amiloride-sensitive Na(+)-selective conductance that is not found in the cells of the secretory endpieces. Since studies on ripped-off outside-out patches from the basolateral membranes of isolated intralobular ducts show that the membrane conductance is not altered by amiloride, it can be inferred that the Na+ conductance seen in whole-cell experiments is located in the luminal membrane. These studies thus provide evidence for the presence of a luminal Na+ conductance in salivary ducts and indicate that intralobular and extralobular ducts may handle Na+ in a similar manner.
