The purpose of this research was to study the effects of Tu-Chung extract (Eucommia ulmoides OLIV.) administration on serum testosterone and the possible mechanisms in hindlimb- suspended rats. 25 five-week old male Wistar rats were used. All rats were randomly divided into two groups : those treated with Tu-Chung extract (Tu-Chung G, n=suspended for 37 days in hindlimb. 1 mg/ml Tu-Chung extract was administered orally once daily at a dose of 1 ml/100 g body weight. Distilled water was administered in a similar way to the control group. The following results were observed :
1. Serum testosterone concentration in Tu-Chung G was significantly higher than in Cont. G (P<0.001) .
2. There was no significant difference between Tu-Chung G and Cont. G in serum LB concentrations.
3. The Testicular cAMP level in Tu-Chung G was significantly higher than that in Cont. G (P<0.01) .
4. 24-h urinary excretion of 17-ketosteroid in Tu-Chung G was significantly higher than that in Cont. G (P<0.001) .
5. There were no significant differences between the two groups in the weights per body weight of the kidneys, adrenal grand and testes. These results suggest that the adininstration of Tu-Chung extract inducing high serum testosterone concentrations in hindlimb-suspended rats might be due to enhanced testicular and adrenal functions, not pituitary.