THE ANDROGEN RECEPTOR MESSENGER-RNA IS UP-REGULATED BY TESTOSTERONE IN BOTH THE HARDERIAN-GLAND AND THUMB PAD OF THE FROG, RANA-ESCULENTA

alpha(32)P-labelled cDNA probe from plasmid containing rat androgen re ceptor (rAR) has been tested in hybridization experiments using RNAs f rom the Harderian gland and thumb pad of the edible frog, Rana esculen ta. Northern blot analysis has shown a high degree of homology between the rAR cDNA and the frog androgen receptor mRNA (fAR mRNA); this has been supported by both the hybridization conditions (high stringency) and the molecular size of fAR mRNA which is quite similar to those de scribed in mammals (9.4 kb). The role of androgens has been further in vestigated with respect to the kinetics of expression of fAR mRNA in i n vivo experiments. In both the Harderian gland and thumb pad, testost erone has increased the levels of fAR mRNA as compared with the untrea ted groups. The use of cyproterone acetate (CPA) in combination with t estosterone has resulted in a loss of the increase in fAR mRNA as comp ared to testosterone-treated groups, while CPA alone has resembled the control group. In primary cultures of frog Harderian gland and thumb pad cells, the steady-state levels of fAR mRNA have been increased in the cells exposed to testosterone as compared to those not exposed. Th ese findings confirm that, in these androgen target tissues, testoster one exerts an up-regulation on its own receptors, increasing the accum ulation of fAR mRNA in the same way as oestrogens up-regulate the expr ession of their own receptors in Xenopus liver and oviduct cells.