OCCURRENCE OF ANDROGEN AND ESTROGEN-RECEPTOR MESSENGER-RNAS IN THE HARDERIAN-GLAND - A COMPARATIVE SURVEY

In Rana esculenta the presence of an androgen receptor in both the mal e and female Harderian gland (HG) has been demonstrated. Hybridization analysis has evidenced a high degree of homology between the rat andr ogen receptor cDNA and the frog androgen receptor mRNA (fARmRNA). Corr espondingly the molecular size of fARmRNA is similar to those describe d in mammals (9.4 kb). In in vivo experiments testosterone (T) increas es the levels of fARmRNA. The use of the antiandrogen alone or in comb ination with T prevents the increase of fARmRNA. In the control animal s a loss of fARmRNA has been observed. In primary cultures of HG cells , the steady-state levels of fARmRNA increase in the cells exposed to T. These results suggest that T exerts an autoinduction on its own rec eptor, increasing the levels of fARmRNA. In Xenopus laevis the HG show s a sexual dimorphism of the protein pattern. The female shows two maj or proteins (210 and 180 kDa). Administration of estradiol to the male shifts the protein pattern into the female one. In this respect an es trogen receptor mRNA (ERmRNA) has been found in the female gland and c an be induced in the male one. No ARmRNA has been detected in either s exes. A similar sex dimorphism has been found in Gallus domesticus. Th e female pattern is characterised by a protein fraction of about 210 k Da, the male one by a protein fraction of about 180 kDa. In 4-day-old chicks no sex differences have been found. An ERmRNA is expressed in t he female, while no ARmRNA has been detected in both sexes. Neither AR nor ER mRNAs have been detected in the chick HG. Among mammals the HG of the hamster (Mesocricetus auratus) shows an androgen-dependent sex dimorphism. In in vitro experiments T 10(-12) M induces a onefold inc rease of ARmRNA with respect to unexposed cells. This effect reaches i ts maximum (4.4-fold) when cells are exposed to T 10(-8) M. The size o f the hamster ARmRNA is similar to that observed in other mammals (9.5 kb). The above results suggest that in the HG the phenomenon of autoi nduction occurs and that there is a relationship between the androgen or estrogen dependence of the HG and the digamety of the species. (C) 1996 Wiley-Liss, Inc.