EFFECT OF GREEN TEA RICH IN GAMMA-AMINOBUTYRIC-ACID ON BLOOD-PRESSUREOF DAHL SALT-SENSITIVE RATS

gamma-Aminobutyric acid (GABA) is known to be involved in the regulati on of blood pressure by modulating the neurotransmitter release in the central and peripheral sympathetic nervous systems. This study invest igated the antihypertensive effect of green tea rich in GABA (GABA-ric h tea) in young and old DahI salt-sensitive (S) rats. GABA-rich tea wa s made by fermenting fresh green tea leaves under nitrogen gas. In exp eriment 1, 21 11-month-old rats, fed a 4% NaCl diet for 3 weeks, were given water (group W), an ordinary tea solution (group T), or a GABA-r ich tea solution (group G) for 4 weeks. The average GABA intake was 4. 0 mg/rat per day. After 4 weeks of the treatment, blood pressure was s ignificantly decreased in group G (176 +/- 4; P < .01) compared with g roup W (207 +/- 9) or group T (193 +/- 5 mm Hg). Plasma GABA levels we re more elevated in group G (111 +/- 54) than in group W (not detectab le) or group T (14 +/- 8 ng/ mL; P < .01 v G). In experiment 2, 21 5-w eek-old rats, fed a 4% NaCl diet, were divided into groups W, T, and G . The average GABA intake was 1.8 mg/rat per day. Body weight or chow and beverage consumption did not differ significantly among the three groups. After 4 weeks of the treatment, although blood pressure was co mparable in groups W and T (165 +/- 3 v 164 +/- 5 mm Hg, mean +/- SE), it was significantly lower in group G (142 +/- 3 mm Hg) than in the o ther groups (P < .01). Plasma aldosterone concentration was increased in group G compared to the other groups. Thus, GABA-rich tea seems not only to decrease the established high blood pressure but to prevent t he development of hypertension in Dahl S rats fed a high salt diet.