EXPRESSION OF THE GENE FOR THE RECEPTOR OF GONADOTROPIN-RELEASING-HORMONE IN THE RAT MAMMARY-GLAND

Recent findings have demonstrated that the GnRH gene is expressed in t he mammary gland of pregnant and lactating rats but not of virgin rats . Indeed, significant concentrations of biologically active GnRH have been found in milk of human, cow, sheep and rat. We have, therefore, l ooked for expression of the GnRH receptor in the rat mammary gland. By reverse transcription (RT)-PCR amplification, we have demonstrated th e presence of GnRH receptor mRNA in mammary gland samples derived from virgin, pregnant and lactating rats. The GnRH receptor transcript clo ned from the mammary gland was sequenced and found to have an identica l coding region to the one cloned from the pituitary gland. In additio n, we have found that the mammary gland, as the pituitary gland, conta ins at least two transcripts having the same coding region but differe nt 5' non-coding regions. Binding studies, however, could demonstrate only low-affinity binding sites. These results, therefore, suggest tha t the regulation of the GnRH receptor occurs posttranscriptionally rat her than at the level of transcription.