Expression of the androgen receptor in the testes and the concentrations of gonadotropins and sex steroid hormones in male turkeys (Meleagris gallopavo) during growth and development

• This study revealed changes in AR expression in testes of growing turkeys.
• Gonadotropins, sex steroid hormones and AR in testes regulate male sexual function.
• The AR protein was found exclusively in the nuclei of testicular somatic cells.
• The 20th week is a key phase in development of reproductive system of male turkeys.

Androgens, including testosterone (T) and androstenedione (A4), are essential for puberty, fertility and sexual functions. The biological activity of those hormones is mediated via the androgen receptor (AR). The regulation of androgen action in birds is poorly understood. Therefore, the present study analysed mRNA and protein expression of AR in the testes, plasma concentrations of the luteinizing hormone (LH), follicle-stimulating hormone (FSH), T, A4 and oestradiol (E2), as well as the levels of T, A4 and E2 in testicular homogenates of male turkeys (Meleagris gallopavo) at the age of 4, 8, 12, 16, 20, 24 and 28 weeks. Plasma concentrations of LH and FSH, as well as plasma and testicular levels of T and A4 began to increase at 20 weeks of age. The lowest plasma levels of E2 were noted at 20 weeks relative to other growth stages. The 20th week of life seems to be the key phase in the development of the reproductive system of turkeys. The AR protein was found in the nuclei of testicular cells in all examined growth stages. Higher expression of AR protein in the testes beginning at 20 weeks of age was accompanied by high plasma concentrations of LH and high plasma and testicular levels of androgens. This relationship seems to be necessary to regulate male sexual function.