Basolateral amiloride-sensitive Na+ transport pathway in rat tongue epithelium

Area of Science:

• Physiology
• Molecular Biology
• Neuroscience

Background:

• A model proposes basolateral Na+ channels in rat lingual epithelium to explain amiloride-insensitive taste responses and ion transport.
• These proposed channels could account for differential amiloride sensitivity with various sodium salts and Na+ diffusion via lateral pathways.

Purpose of the Study:

• To experimentally test for the presence of amiloride-sensitive Na+ channels in the basolateral membrane of rat dorsal tongue epithelium.
• To investigate the characteristics and function of these potential basolateral Na+ channels in lingual ion transport.

Main Methods:

• Utilized an in vitro preparation of rat anterior-dorsal tongue epithelium, with connective tissue removed via enzyme digestion.
• Employed voltage-clamp techniques and a modified Ussing chamber to measure transepithelial short-circuit current (Isc).
• Administered amiloride in the submucosal solution to assess its inhibitory effects on Isc.

Main Results:

• Submucosal amiloride application reduced Isc, with a higher inhibition constant (Ki) of 52 microM compared to apical channels.
• Observed reduced selectivity for Na+ over K+ (ratio of 1-3) for submucosal amiloride inhibition compared to mucosal amiloride.
• Inhibition of Isc by submucosal amiloride increased with higher mucosal NaCl concentrations and was minimal with sodium gluconate.

Conclusions:

• The results strongly support the existence of amiloride-sensitive Na+ channels in the basolateral membranes of rat dorsal tongue epithelium.
• These findings are consistent with the proposed model involving basolateral Na+ channels in taste cells for ion transport and taste perception.