Generation of hypophysiotropic activity in hypothalamic extracts in vitro.

Area of Science:

• Neuroendocrinology
• Reproductive Biology

Background:

• The hypothalamus regulates crucial endocrine functions, including the release of gonadotropins and prolactin.
• Understanding the storage and activation mechanisms of hypothalamic releasing and inhibiting factors is vital for reproductive health research.

Purpose of the Study:

• To investigate the extraction conditions influencing the activity of hypothalamic factors controlling luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin (PRL) release.
• To determine if LH/FSH releasing factors and PRL release-inhibiting components are stored in an active or inactive form.

Main Methods:

• Extraction of rat hypothalami using neutral aqueous and acid ethanolic methods.
• Assay of LH and FSH releasing activity and PRL release-inhibiting activity in the extracts.
• Ultrafiltration of neutral extracts and subsequent acidification to assess activity changes.

Main Results:

• LH and FSH releasing activities were detected only in acid ethanolic extracts.
• PRL release-inhibiting activity was present in both neutral and acid extracts.
• Acidification of neutral ultrafiltrates induced LH/FSH releasing activity, suggesting activation from an inactive precursor.

Conclusions:

• Hypothalamic LH and FSH releasing factors appear to be stored in an inactive precursor form, requiring acidic conditions for in vitro activation.
• The component(s) inhibiting PRL release are active under both neutral and acidic conditions, indicating a different storage/activation mechanism compared to gonadotropin factors.