Characterization of estrogen and glucocorticoid receptors, skeletal muscle protein turnover and tissue growth in lambs treated with trenbolone acetate and estradiol

Abstract

A study was conducted to determine the effects of trenbolone acetate (TBA) and estradiol-17B (E2) implantation on the characteristics of the glucocorticoid and E2 receptor, skeletal muscle protein turnover and tissue growth. Twenty-four lambs were utilized. Trenbolone acetate did not ,affect (P>.10) degradation rates in the semitendinosus (ST) and triceps brachii (TB) muscles, the production of cortisol, adrenal weights and cytosolic glucocorticoid binding capacity (Bmax). Trenbolone acetate decreased synthesis rate of muscle protein (P<.Ol), the percent of [3H] dexamethasone binding in the nuclear fraction, Bmax and the disociation constant (Kd) of the cytosolic E2 receptor, only in the TB muscle.

Deoxyribonucleic acid (DNA) of the TB was increased (P<.05) with TBA. Pituitary weights were decreased (P<.005) with TBA and increased (P<.Ol) with E2. Estradiol decreased (P<.05) Bmax of the cytosolic E2 receptor in the ST and decreased (P<.05) Bmax of the nuclear E2 receptor in the TB muscle. The TB muscle had greater (P<.05) synthesis rates than the ST and the protein:RNA ratio was decreased (P<.05) in the TB. The TB muscle had greater (P<.005) Bmax for the cytosolic glucocorticoid receptor.