Antidiuretic peptide in mammalian choroid plexus

Area of Science:

• Neuroendocrinology
• Biochemistry

Background:

• Choroid plexuses (CP) from various species contain antidiuretic activity.
• The precise nature and localization of this activity remain incompletely understood.

Purpose of the Study:

• To isolate and characterize the antidiuretic factor present in bovine choroid plexus.
• To determine the biochemical properties and biological potencies of the purified factor.

Main Methods:

• Extraction and purification of the antidiuretic factor using acetic acid, acetone, ethyl ether, gel filtration (Sephadex G-25), and paper chromatography.
• Assessment of antidiuretic activity in anesthetized-hydrated rats.
• Determination of pressor and oxytocic potencies in anesthetized rats and isolated rat uteri, respectively.
• Enzymatic and chemical degradation studies to elucidate the factor's composition.

Main Results:

• A 100-fold concentration of the antidiuretic factor was achieved.
• The purified fraction (IIgammaB2) has a molecular weight between 750 and 3,500.
• Antidiuretic activity was sensitive to trypsin, performic acid, and thioglycollic acid, indicating a peptide or protein nature.
• The factor demonstrated antidiuretic (1.9 U/mg), pressor (0.5 U/mg), and oxytocic (0.1 U/mg) potencies.

Conclusions:

• Bovine choroid plexus contains a potent, relatively small peptide or protein with significant antidiuretic, pressor, and oxytocic activities.
• The purification and characterization provide insights into the neuroendocrine functions of the choroid plexus.