Question: 

Garlic is known as a natural remedy for cardiovascular diseases, such as hypertension. However, there is still lack of molecular data, which would explain garlic effects. The regulation of blood pressure depends inter alia on sodium retention in the distal kidney and thus on the activity of epithelial sodium channels (ENaCs). Therefore we questioned if there is any impact of garlic and its main compounds on ENaCs.

Methodology: 

Human ENaCs, consisting of the a, b, and g subunits, were heterologously expressed in Xenopous laevis oocytes and exposed to garlic extract (GE) or garlic compounds. Transmembrane currents (I_M) of ENaC-expressing oocytes were electrophysiologically measured by the two-electrode-voltage-clamp technique. GE was made from 5 g of fresh garlic in 10 ml oocyte ringer solution on ice for 1 h and was then filtered to get a water soluble GE.

Results: 

The application of 1% GE decreased I_M of ENaC-expressing oocytes by ~80% and had no effect on I_M of control-oocytes. The effect was not reversible and sensitive to the specific ENaC inhibitor amiloride. The effect of GE was reduced by 10 mM dithiothreitol or 20 mM L-cysteine, indicating that the effect is thiol-dependent. Comparable to GE, allicin (100 mM), the main thiol-reactive garlic compund, decreased I_M of ENaC-expressing oocytes.

Conclusion: 

These data indicate that thiol-reactive compounds from GE irreversibly inhibit ENaCs. A garlic-mediated decrease of sodium reabsorption might explain hypotensive effects of garlic as a result of enhanced natriuresis and diuresis in the kidney.