Recent findings have demonstrated that the GnRH gene is expressed in the 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, looked for expression of the GnRH receptor in the rat mammary gland. By reverse transcription (RT)-PCR amplification, we have demonstrated the presence of GnRH receptor mRNA in mammary gland samples derived from virgin, pregnant and lactating rats. The GnRH receptor transcript cloned from the mammary gland was sequenced and found to have an identical coding region to the one cloned from the pituitary gland. In addition, we have found that the mammary gland, as the pituitary gland, contains at least two transcripts having the same coding region but different 5' non-coding regions, Binding studies, however, could demonstrate only low-affinity binding sites. These results, therefore, suggest that the regulation of the GnRH receptor occurs posttranscriptionally rather than at the level of transcription.
Bibliographical noteFunding Information:
Acknowledgements: We thank Dr. K. Eidne for providing the rat pituitary GnRH receptor cDNA, Drs. M. Fridkin and F. Kohen for helpful discussions, Mrs. R. Levin and Mrs. M. Kopelowitz for excellent secretarial assistance. This work was supported by the German Israeli Foundation for Scientific Research and Development (GIF) and by the Marc Levine Fund. Y.K. is the incumbent of the Adlai E. Stevenson Ill Chair of Endocrinology and Reproductive Biology.
- LHRH/GnRH receptor transcript
- Mammary gland (rat)