TY - JOUR
T1 - Relative binding affinity of anabolic-androgenic steroids
T2 - Comparison of the binding to the androgen receptors in skeletal muscle and in prostate, as well as to sex hormone-binding globulin
AU - Saartok, Tönu
AU - Dahlberg, Erik
AU - Gustafsson, Jan-Ake
PY - 1984/1/1
Y1 - 1984/1/1
N2 - It is unclear whether anabolic steroids act on skeletal muscle via the androgen receptor (AR) in this tissue, or whether there is a separate anabolic receptor. When several anabolic steroids were tested as competitors for the binding of [3H]methyltrienolone (MT; 17β-hydroxy-17α-methyl-4,9,11-estratrien-3-one) to the AR in rat and rabbit skeletal muscle and rat prostate, respectively, MT itself was the most efficient competitor. 1α-Methyl-5α-dihydrotestosterone (1α-methyl-DHT; mesterolone) bound most avidly to sex hormone-binding globulin (SHBG) [relative binding affinity (RBA) about 4 times that of DHT]. Some anabolic-androgenic steroids bound strongly to the AR in skeletal muscle and prostate [RBAs relative to that of MT: MT > 19-nortestosterone (NorT; nandrolone) > methenolone (17β-hydroxy-1-methyl-5α-androst-1-en-3-one) > testosterone (T) > 1α-methyl-DHT]. In other cases, AR binding was weak (RBA values < 0.05): stanozolol (17α-methyl-5α-androstano[3,2-c]pyrazol-17β-ol), methanedienone (17β-hydroxy-17α-methyl-1,4-androstadien-3-one), and fluoxymesterolone (9α-fluoro-11β-hydroxy-17α-methyl-T). Other compounds had RBAs too low to be determined (e.g. oxymetholone (17β-hydroxy-2-hydroxymethylene-17α-methyl-5α-androstane-3-one) and ethylestrenol (17α-ethyl-4-estren-17β-ol). The competition pattern was similar in muscle and prostate, except for a higher RBA of DHT in the prostate. The low RBA of DHT in muscle was probably due to the previously reported rapid reduction of its 3-keto function to metabolites, which did not bind the AR [5α-androstane-3α,17β-diol and its 3β-isomer (3α- and 3β-adiol, respectively)]. Some anabolic-androgenic steroids (only a few synthetic) bound to SHBG (1α-methyl-DHT >> DHT > T > 3β-adiol > 3α-adiol = 17α-methyl-T > methenolone > methanedienone > stanozolol). The ratio of the RBA in rat muscle to that in the prostate (an estimate of the myotrophic potency of the compounds) was close to unity, varying only between about 0.4 and 1.7 in most cases. The present data indicate that 1) the existence of a putative anabolic receptor distinct from the AR must be questioned, 2) many anabolic steroids interact with the AR (generally with lower RBA than NorT or T), 3) some steroids with anabolic-androgenic activity in vivo do not bind to the AR, and must have an indirect mechanism of action (e.g. via biotransformation to active compounds, by influence the metabolism of other steroid, or by displacing them from SHBG).
AB - It is unclear whether anabolic steroids act on skeletal muscle via the androgen receptor (AR) in this tissue, or whether there is a separate anabolic receptor. When several anabolic steroids were tested as competitors for the binding of [3H]methyltrienolone (MT; 17β-hydroxy-17α-methyl-4,9,11-estratrien-3-one) to the AR in rat and rabbit skeletal muscle and rat prostate, respectively, MT itself was the most efficient competitor. 1α-Methyl-5α-dihydrotestosterone (1α-methyl-DHT; mesterolone) bound most avidly to sex hormone-binding globulin (SHBG) [relative binding affinity (RBA) about 4 times that of DHT]. Some anabolic-androgenic steroids bound strongly to the AR in skeletal muscle and prostate [RBAs relative to that of MT: MT > 19-nortestosterone (NorT; nandrolone) > methenolone (17β-hydroxy-1-methyl-5α-androst-1-en-3-one) > testosterone (T) > 1α-methyl-DHT]. In other cases, AR binding was weak (RBA values < 0.05): stanozolol (17α-methyl-5α-androstano[3,2-c]pyrazol-17β-ol), methanedienone (17β-hydroxy-17α-methyl-1,4-androstadien-3-one), and fluoxymesterolone (9α-fluoro-11β-hydroxy-17α-methyl-T). Other compounds had RBAs too low to be determined (e.g. oxymetholone (17β-hydroxy-2-hydroxymethylene-17α-methyl-5α-androstane-3-one) and ethylestrenol (17α-ethyl-4-estren-17β-ol). The competition pattern was similar in muscle and prostate, except for a higher RBA of DHT in the prostate. The low RBA of DHT in muscle was probably due to the previously reported rapid reduction of its 3-keto function to metabolites, which did not bind the AR [5α-androstane-3α,17β-diol and its 3β-isomer (3α- and 3β-adiol, respectively)]. Some anabolic-androgenic steroids (only a few synthetic) bound to SHBG (1α-methyl-DHT >> DHT > T > 3β-adiol > 3α-adiol = 17α-methyl-T > methenolone > methanedienone > stanozolol). The ratio of the RBA in rat muscle to that in the prostate (an estimate of the myotrophic potency of the compounds) was close to unity, varying only between about 0.4 and 1.7 in most cases. The present data indicate that 1) the existence of a putative anabolic receptor distinct from the AR must be questioned, 2) many anabolic steroids interact with the AR (generally with lower RBA than NorT or T), 3) some steroids with anabolic-androgenic activity in vivo do not bind to the AR, and must have an indirect mechanism of action (e.g. via biotransformation to active compounds, by influence the metabolism of other steroid, or by displacing them from SHBG).
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U2 - 10.1210/endo-114-6-2100
DO - 10.1210/endo-114-6-2100
M3 - Article
C2 - 6539197
AN - SCOPUS:0021233846
VL - 114
SP - 2100
EP - 2106
JO - Endocrinology
JF - Endocrinology
SN - 0013-7227
IS - 6
ER -