Intermedin functions as a pituitary paracrine factor regulating prolactin release

Area of Science:

• Endocrinology
• Neuroendocrinology
• Molecular Biology

Background:

• Calcitonin gene-related peptide family peptides are vital for homeostasis.
• Intermedin (IMD) is a newly identified member of this family, found in various vertebrate organs, including the pituitary.
• IMD's presence in the pituitary suggests a potential role in regulating hormone secretion.

Purpose of the Study:

• To investigate the role of Intermedin (IMD) in the pituitary.
• To determine if IMD functions as a paracrine factor regulating anterior pituitary hormone secretion.
• To explore the relationship between IMD, estrogen, and prolactin regulation during reproduction.

Main Methods:

• Real-time PCR and immunohistochemistry to analyze IMD expression in rat pituitaries.
• Quantitative and in situ hybridization to detect IMD receptor transcripts.
• In vitro studies using cultured pituitary cells and in vivo studies in conscious rats to assess IMD's effect on prolactin release.
• Analysis of IMD gene promoter activity in response to estrogen treatment.

Main Results:

• IMD is expressed in the pituitary intermediate lobe and select adrenocorticotrophs.
• IMD treatment dose-dependently increased prolactin release in vitro and in vivo, with minimal effects on other pituitary hormones.
• Pituitary IMD expression significantly increased in lactating rats and decreased in ovariectomized rats, with estrogen/diethylstilbestrol restoring expression.
• The IMD gene promoter contains estrogen response elements, and estrogen up-regulates its activity.

Conclusions:

• Intermedin (IMD) is a novel, estrogen-dependent prolactin-releasing factor secreted by the pituitary intermediate lobe.
• IMD plays a significant role in regulating prolactin release, particularly during female reproduction.
• These findings highlight IMD as a key factor in the neuroendocrine control of reproduction.