ESTROGEN CONTROL OF THE SEXUAL DIMORPHISM IN THE HARDERIAN-GLAND OF XENOPUS-LAEVIS

Xenopus laevis shows a sexual dimorphism of the electrophoretic patter n of Harderian gland (HG) proteins. The male pattern displays three pr otein fractions whose molecular sizes are approx. 205, 180 and 78 kDa, respectively, and which are absent in the female pattern. Conversely, the female pattern displays two protein fractions of approx. 190 and 76 kDa, respectively. This sexual dimorphism led us to hypothesize a s ex steroid control of the HG. Administration of 17 beta-oestradiol to male Xenopus converts the male protein pattern into the female one, wh ile the administration of testosterone to the female has no effect. In this respect neither Northern analysis nor the RNase-protection assay performed using a 213 bp encoding for the androgen-binding domain rev eals the presence of an androgen receptor mRNA in Xenopus HG. Converse ly, Northern analysis has shown an oestrogen receptor mRNA whose size is approx. 6.5 kb and the RNase-protection assay performed by using a 197 bp encoding for the oestrogen-binding domain has also displayed th e presence of an oestrogen receptor mRNA in the female HG but not in t he male one. In addition, the oestrogen administration to male Xenopus induces the appearance of an oestrogen receptor mRNA. Androgen admini stration to female toad is ineffective. Taken together, all these find ings suggest that in Xenopus laevis oestrogens are involved into the H G physiology. The appearance of an oestrogen receptor mRNA in the oest radiol treated males supports the hypothesis of the occurrence of auto induction of oestrogen receptor mRNA expression in the HG. (C) 1997 Pu blished by Elsevier Science Ltd. All rights reserved.