Comparison of the Effects of Three Tea Cultivars ( Camellia sinensis L.) on Nitric Oxide Production and Aortic Soluble Guanylate Cyclase Expression in High-Salt Diet-Fed Spontaneously Hypertensive Rats

: Studies have suggested that the consumption of green tea reduces the risk of cardiovascular diseases. Although epigallocatechin gallate (EGCG) is the best studied active substance characteristic of green tea, previous results on EGCG do not appear sufficient to explain completely the mechanism of cardiovascular protection by green tea. Therefore, we investigated the effect of three different tea cultivars, "Yabukita," "Sofu," and "Sunrouge," which have characteristic flavonoid compositions, on the nitric oxide (NO) production and the related protein expression in the aorta of spontaneously hypertensive rats (SHRs) fed a high-salt diet. As a result, the reduction of urinary NO metabolite (NOx) levels, which reflect whole-body NO production, caused by the high-salt diet were significantly prevented by all three tea infusions. The improvement of NOx reduction in the tea-intake groups was unlikely to be caused by the changes in oxidative damage. On the other hand, as a partial effect, only "Yabukita" or "Sofu" increased the expression of the soluble guanylate cyclase, a receptor for NO, in the thoracic aorta. In the present study, the differences in the composition of these three cultivars led to partially different effects on NO signaling in SHRs, suggesting the physiological significance of subdominant ingredients besides EGCG.