AJP - Endocrinology and Metabolism, Vol 268, Issue 6 E1077-E1082, Copyright © 1995 by American Physiological Society
Sexual dimorphism in the growth response of entire and gonadectomized rats to clenbuterol
M. N. Sillence, M. M. Reich and B. C. Thomson
Commonwealth Scientific and Industrial Research Organization, Division of Tropical Animal Production, Tropical Beef Centre, Rockhampton, Queensland, Australia.
This study compared the anabolic effects of clenbuterol in male and female
rats and determined the relative contribution of testicular and ovarian
hormones to any observed gender difference. Seventy-two 12-wk-old rats were
used in a 2 x 2 x 2 factorial design in which animals were either male or
female, entire or gonadectomized at 3 wk of age, and fed either a control
diet or a diet containing 4 mg clenbuterol/kg feed for 8 days. Compared
with entire male rats, entire females gained 64% less weight, had lighter
carcasses (-36%) and gastrocnemius muscles (-62%), and had higher plasma
concentrations of the catabolic hormone corticosterone (P < 0.05).
Castration had a negative effect on growth in male rats, and ovariectomy
had a positive effect in females, but there was still a gender difference
in body weight between gonadectomized males and females, which amounted to
34% of the gender difference observed in intact rats. The density of beta
2-adrenoceptors in skeletal muscle was not different between males and
females, nor was it affected by gonadectomy. Clenbuterol increased both
weight gain and gastrocnemius muscle weight, with the latter response in
entire and castrated male rats (+ 1.31 and + 1.17 g) being more than double
that seen in entire and ovariectomized females (+ 0.58 and + 0.55 g). The
downregulation response of beta 2-adrenoceptors in this muscle was
remarkably consistent in all treated groups (-50% to -53%).(ABSTRACT
TRUNCATED AT 250 WORDS)
