Inhibition of aromatase activity by green tea extract catechins and their endocrinological effects of oral administration in rats.
We orally administered polyphenone-60 (P-60), green tea extract catechins, in the diet (0, 1.25 and 5%) to male rats for 2, 4 and 8 weeks initiated at 5 weeks old. It was found that a 5% dose to male rats for 2-8 weeks induced goiters and decreased weights of the body, testis and prostate gland. Endocrinologically, elevating plasma thyroid stimulating hormone (TSH), luteinizing hormone (LH) and testosterone levels and decreasing tri-iodothyronine (T(3)) and thyroxine (T(4)) levels were induced by this treatment. We also found that P-60 as a whole and some of its constituents exhibited inhibitory effects on human placental aromatase activity by in vitro assay. The concentration of P-60 that required producing 50% inhibition of the aromatase activity (IC(50) value) was 28 microg/ml. The IC(50) values of (-)-catechin gallate (Cg), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCg) and (-)-gallocatechin gallate (GCg) were 5.5 x 10(-6), 1.0 x 10(-4), 6.0 x 10(-5) and 1.5 x 10(-5) M, respectively. (-)- Epicatechin gallate (ECg) at 1.0 x 10(-4) M produced 20% inhibition. (-)-Epicatechin (EC) and (+)-catechin (CT) exhibited no effects on aromatase activity. The endocrinological changes observed in vivo were in conformity with antithyroid effects and aromatase inhibition effects of P-60 and its constituents.
Satoh
K
K
Department of Toxicology, The Tokyo Metropolitan Research Laboratory of Public Health, 24-1 Hyakunincho 3 chome, Shinjuku-ku, Japan. sato@tokyo-eiken.go.jp
Sakamoto
Y
Y
Ogata
A
A
Nagai
F
F
Mikuriya
H
H
Numazawa
M
M
Yamada
K
K
Aoki
N
N
D000284:Administration, Oral; D000818:Animals; D047072:Aromatase Inhibitors; D005640:Follicle Stimulating Hormone / Q000097:blood; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D009929:Organ Size / Q000187:drug effects; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011916:Rats, Inbred F344; D013662:Tea / Q000737:chemistry*; D013739:Testosterone / Q000097:blood; D013963:Thyroid Hormones / Q000097:blood; D013972:Thyrotropin / Q000097:blood
D047072:Aromatase Inhibitors; D010936:Plant Extracts; D013662:Tea; D013963:Thyroid Hormones; D013739:Testosterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin