Decidual-type prolactin expression by the human myometrium

Area of Science:

• Reproductive Biology
• Endocrinology
• Molecular Genetics

Background:

• The human myometrium has been proposed as a potential source of uterine prolactin (PRL).
• Immunoreactive PRL has been detected in myometrial explant culture supernatants.
• The precise nature and regulation of PRL production in the myometrium remain to be fully elucidated.

Purpose of the Study:

• To investigate the expression and characteristics of human prolactin (hPRL) in the human myometrium.
• To determine if the myometrium synthesizes PRL and to characterize its transcript and protein.
• To examine the regulation of myometrial hPRL expression by hormones like progestin and estrogen.

Main Methods:

• Northern blot hybridization to detect hPRL mRNA in myometrium.
• Sequence and primer extension analyses to characterize the hPRL transcript.
• Myometrial explant cultures to assess hPRL secretion and regulation.
• Nb2 lymphoma bioassay to determine lactogenic activity.
• Monoclonal antibody neutralization assays.

Main Results:

• The human (h) PRL gene is expressed in the myometrium in vivo, with a transcript larger than pituitary hPRL mRNA.
• Myometrial PRL is identical to pituitary hPRL, but the mRNA originates from alternative transcription initiation.
• Myometrial explants secrete hPRL, including a glycosylated variant (G-hPRL), with significant lactogenic activity.
• hPRL secretion and mRNA abundance are markedly reduced by progestin (medroxy-progesterone acetate) but unaffected by estrogen.

Conclusions:

• The human myometrium is a source of hPRL, utilizing an alternative mRNA transcript.
• Myometrial hPRL production is regulated by progestin, indicating a potential role in uterine function.
• These findings expand our understanding of PRL's extrapituitary sources and regulation within the uterus.