Introduction Male marmosets present a potentially useful model for study of the regulation of testicular function in humans. In both humans and marmosets the testes are descended into the scrotum at the time of birth and a period of neonatal testicular activity characterized by a transient increase (‘neonatal surge’) in plasma testosterone concentrations (Forest et al., 1976; Dixson, 1986; Lunn et al., 1994) and Sertoli cell proliferation (Cortes et al., 1987; Sharpe et al., 2000) is followed by a relatively quiescent and extended ‘childhood’ or ‘infancy’ phase. In both marmosets (Sharpe Comparison of androgen receptor and oestrogen receptor β 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 C. McKinnell 1 , P. T. K. Saunders 1 , H. M. Fraser 1 , C. J. H. Kelnar 2 , C. Kivlin 1 , K. D. Morris 1 and R. M. Sharpe 1 1 MRC Human Reproductive Sciences Unit, Centre for Reproductive Biology, 37 Chalmers Street, Edinburgh EH3 9ET, UK; and 2 Section of Child Life and Health, Department of Reproductive and Developmental Sciences, University of Edinburgh, Edinburgh EH9 1UW, UK Reproduction (2001) 122, 419–429 Research The aims of this study were: (i) to investigate the cellular immunoexpression of androgen receptor and oestrogen receptor β in the testes of the common marmoset (Callithrix jacchus) during neonatal life compared with their expression at later ages; (ii) to establish whether neonatal marmoset Sertoli cells are targets for androgens or oestrogens or both; and (iii) to investigate the relation- ship between neonatal plasma testosterone concentrations and androgen receptor immunoexpression by abolishing the neonatal testosterone surge with a potent GnRH antagonist. Androgen receptor and oestrogen receptor β immunoexpression were evaluated in neonatal animals aged 1–4 days, 4 weeks and 6 weeks, and compared with immunoexpression in animals aged 18–22 weeks (early infancy), 35 weeks (late infancy), 58–62 weeks (late pubertal) and > 100 weeks (adult). Immunoexpression of androgen receptor in the reproductive tract was also evaluated at each age. Sertoli cell immunoexpression of androgen receptor was weak or absent in neonatal animals, but increased substantially in infant animals, reaching adult levels by the end of infancy. In contrast, immunoexpression of androgen receptor during the neonatal period was strong in testicular interstitial cells and very strong in epithelial cell nuclei throughout the reproductive tract, and did not change greatly with age in these cells or tissues. Similarly, immunoexpression of oestrogen receptor β was prominent in many Sertoli cells and in the germ cells of neonatal animals, and was relatively constant throughout life. Weak immunoexpres- sion 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 immuno- expression was associated with baseline (approximately 0.12 ng ml –1 ) testosterone concentrations in infant animals and with > 10 ng ml –1 in late pubertal and adult animals. Immunoexpression of androgen receptor and oestrogen receptor β was also evaluated in co-twin males aged 4 and 35 weeks, after treatment from birth to 4 weeks or from week 25 to week 35, respectively, with either vehicle or with GnRH antagonist at a dose known to suppress the neonatal testosterone surge completely. Only GnRH antagonist treatment during weeks 25–35 reduced androgen receptor immunoexpression, whereas immuno- expression of oestrogen receptor β was unaffected by treatment during either period. On the basis of these findings it is suggested that: (i) neonatal marmoset Sertoli cells may be targets primarily for oestrogens rather than androgens; (ii) androgen receptor expression in the testes of neonatal and infant marmosets is not regulated in a straightforward way by testosterone; and (iii) high neonatal concentrations of plasma testosterone are not absolutely necessary for expression of androgen receptor in marmoset testes at this time. © 2001 Journals of Reproduction and Fertility 1470-1626/2001 Email: c.mckinnell@hrsu.mrc.ac.uk Downloaded from Bioscientifica.com at 06/07/2020 09:14:59PM via free access