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Black and Green Tea Polyphenols Attenuate Blood Pressure Increases in Stroke-Prone Spontaneously Hypertensive Rats1


ABSTRACT

Oxidative stress was reported to be involved not only in
cardiovascular diseases, but also in hypertension. Epidemiologic
studies indicated that tea consumption slightly reduces blood pressure.
We conducted two studies to determine whether black and green tea can
lower blood pressure (BP) in stroke-prone spontaneously hypertensive
rats (SHRSP). Male SHRSP (n = 15) were allowed to recover for 2 wk
after a transmitter for measuring BP was implanted in the peritoneal
cavity. The rats were divided into three groups: the control group
consumed tap water (30 mL/d); the black tea polyphenol group (BTP)
consumed water containing 3.5 g/L thearubigins,0.6 g/L theaflavins, 0.5
g/L flavonols and 0.4 g/L catechins; and the green tea polyphenol group
(GTP) consumed water containing 3.5 g/L catechins, 0.5 g/L flavonols
and 1 g/L polymetric flavonoids. The telemetry system was used to
measure BP, which were recorded continuously every 5 min for 24 h.
During the daytime, systolic and diastolic BP were significantly lower
in the BTP and GTP groups than in the controls. Protein expressions of
catalase and phosphorylated myosin light chain (MLC-p) were measured in
the aorta by Western blotting. GTP significantly increased catalase
expression, and BTP and GTP significantly decreased MLC-p expression in
the aorta. These data demonstrate that both black and green tea
polyphenols attenuate blood pressure increases through their
antioxidant properties in SHRSP. Furthermore, because the amounts of
polyphenols used in this experiment correspond to those in ~1 L of tea,
the regular consumption of black and green tea may also provide some
protection against hypertension in humans. J. Nutr. 134: 38-42, 2004.

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