Comparison of androgen receptor and oestrogen receptor beta immunoexpression in the testes of the common marmoset (Callithrix jacchus) from birth to adulthood: low androgen receptor immunoexpression in Sertoli cells during the neonatal increase in testosterone concentrations

The aims of this study were: (i) to investigate the cellular immunoexpressi on of androgen receptor and oestrogen receptor beta in the testes of the co mmon marmoset (Callithrix jacchus) during neonatal life compared with their expression at later ages; (ii) to establish whether neonatal marmoset Sert oli cells are targets for androgens or oestrogens or both; and (iii) to inv estigate the relationship between neonatal plasma testosterone concentratio ns and androgen receptor immunoexpression by abolishing the neonatal testos terone surge with a potent GnRH antagonist. Androgen receptor and oestrogen receptor beta immunoexpression were evaluated in neonatal animals aged 1-4 days, 4 weeks and 6 weeks, and compared with immunoexpression in animals a ged 18-22 weeks (early infancy), 35 weeks (late infancy), 58-62 weeks (late pubertal) and > 100 weeks (adult). Immunoexpression of androgen receptor i n the reproductive tract was also evaluated at each age. Sertoli cell immun oexpression of androgen receptor was weak or absent in neonatal animals, bu t increased substantially in infant animals, reaching adult levels by the e nd of infancy. In contrast, immunoexpression of androgen receptor during th e neonatal period was strong in testicular interstitial cells and very stro ng in epithelial cell nuclei throughout the reproductive tract, and did not change greatly with age in these cells or tissues. Similarly, immunoexpres sion of oestrogen receptor beta was prominent in many Sertoli cells and in the germ cells of neonatal animals, and was relatively constant throughout life. Weak immunoexpression of androgen receptor in neonatal Sertoli cells was associated with high plasma testosterone concentrations (2.7-5.5 ng ml( -1)), whereas strong Sertoli cell immunoexpression was associated with base line (approximately 0.12 ng ml(-1)) testosterone concentrations in infant a nimals and with > 10 ng ml(-1) in late pubertal and adult animals. Immunoex pression of androgen receptor and oestrogen receptor beta was also evaluate d in co-twin males aged 4 and 35 weeks, after treatment from birth to 4 wee ks or from week 25 to week 35, respectively, with either vehicle or with Gn RH antagonist at a dose known to suppress the neonatal testosterone surge c ompletely. Only GnRH antagonist treatment during weeks 25-35 reduced androg en receptor immunoexpression, whereas immunoexpression of oestrogen recepto r beta was unaffected by treatment during either period. On the basis of th ese findings it is suggested that: (i) neonatal marmoset Sertoli cells may be targets primarily for oestrogens rather than androgens; (ii) androgen re ceptor expression in the testes of neonatal and infant marmosets is not reg ulated in a straightforward way by testosterone; and (iii) high neonatal co ncentrations of plasma testosterone are not absolutely necessary for expres sion of androgen receptor in marmoset testes at this time.