Preliminary evidence for a human prolactin releasing factor

Area of Science:

• Endocrinology
• Molecular Biology
• Biochemistry

Background:

• Human plasma contains factors influencing pituitary hormone release.
• Prolactin and Thyroid-Stimulating Hormone (TSH) are key pituitary hormones with distinct regulatory pathways.

Purpose of the Study:

• To investigate the presence and characteristics of a prolactin-releasing factor (PRF) in normal human plasma.
• To determine if the identified factor is heat-stable and filterable.

Main Methods:

• Plasma extraction using a 3-phase methanol process.
• In vitro incubation of rat anterior pituitary tissue with plasma extracts.
• Assessment of prolactin and TSH release in response to extracts.
• Heat stability and ultra-filtration assays.
• Testing for Thyrotropin-Releasing Hormone (TRH) immunoreactivity.

Main Results:

• Plasma extracts demonstrated a dose-dependent increase in prolactin release, with no effect on TSH release.
• The prolactin-releasing activity remained after heating to 100°C for 10 minutes and ultra-filtration.
• Incubation of plasma did not diminish the PRF activity.
• The extract showed no TRH immunoreactivity.

Conclusions:

• Evidence supports the existence of a circulating prolactin-releasing factor (PRF) in human plasma.
• This PRF is heat-stable and ultra-filterable, distinguishing it from TRH.
• The precise origin of this circulating PRF in human plasma is currently unknown.