Salt- and angiotensin II-dependent variations in amiloride-sensitive rectal potential difference in mice

Area of Science:

• Physiology
• Nephrology
• Gastroenterology

Background:

• Sodium reabsorption in the rectum and distal nephron is primarily mediated by the amiloride-sensitive epithelial sodium channel (ENaC).
• ENaC activity is electrogenic, establishing an amiloride-sensitive transepithelial potential difference (PD).

Purpose of the Study:

• To investigate salt- and Angiotensin II (AngII)-dependent variations in amiloride-sensitive rectal PD in mice.
• To assess the relationship between rectal sodium transport and renal sodium handling.

Main Methods:

• In vivo measurement of amiloride-sensitive rectal PD in mice under varying sodium diets (medium, low, high).
• Assessment of circadian cyclicity in rectal PD.
• Correlation analysis with urinary Na+/K+ ratio and renal sodium handling (lithium clearance technique).
• Evaluation of AngII effects using AT1 receptor antagonists.

Main Results:

• A significant circadian cyclicity in amiloride-sensitive rectal PD was observed, with higher values in the afternoon.
• Rectal PD varied inversely with dietary sodium intake, increasing on low-sodium and decreasing on high-sodium diets.
• Amiloride-sensitive rectal PD strongly correlated with urinary Na+/K+ ratio and distal nephron sodium reabsorption.
• AngII administration decreased rectal PD, an effect attenuated by AT1 receptor blockade.

Conclusions:

• Mouse rectal sodium transport exhibits salt-dependent daily cyclicity, mirroring circadian changes in renal sodium handling.
• Angiotensin II plays a role in modulating the diurnal pattern of rectal amiloride-sensitive sodium transport.