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Immunoreactive dynorphin A-like material in extracted human hypothalamic-hypophysial plasma
S Spampinato1, R Paradisi, M Canossa
1Department of Pharmacology, University of Bologna, Italy.
Insights
Human plasma contains immunoreactive dynorphin A-like material (ir-dyn A). Levels in hypothalamic-pituitary plasma were significantly higher during surgery, suggesting a role in regulating these functions.
Area of Science:
- Neuroendocrinology
- Peptide Hormone Research
Background:
- Dynorphin A is an endogenous opioid peptide with potential roles in the central nervous system.
- Previous studies have indicated dynorphin's involvement in regulating pituitary hormone release.
Purpose of the Study:
- To measure immunoreactive dynorphin A-like material (ir-dyn A) in human plasma.
- To investigate the source and potential function of ir-dyn A in the hypothalamic-pituitary axis.
Main Methods:
- Radioimmunoassay (RIA) for quantifying ir-dyn A in plasma.
- Reverse-phase high-performance liquid chromatography (rp-HPLC) for characterizing dynorphin forms.
- Plasma sampling from peripheral circulation and the hypothalamic-hypophysial region during surgery.
Main Results:
- Consistent ir-dyn A levels (20-40 fmol/ml) were found in peripheral plasma of volunteers and pituitary adenoma patients.
- Hypothalamic-hypophysial plasma showed 4-5 times higher ir-dyn A levels compared to peripheral plasma post-tumor removal.
- rp-HPLC identified dyn A-(1-32) as the major form in peripheral plasma, while hypothalamic-hypophysial plasma contained predominantly dyn A-(1-17).
Conclusions:
- Dynorphin A-related peptides are present in human hypothalamic-hypophysial plasma.
- These peptides may play a role in regulating human hypothalamic and/or pituitary functions.
- The distinct forms of dynorphin found in different plasma compartments suggest localized processing and release.
Abstract:
Immunoreactive dynorphin A-like material (ir-dyn A) in human plasma was measured by a validated radioimmunoassay. In peripheral plasma extracts mean concentrations between 20 and 40 fmol/ml were determined in volunteers and in patients with pituitary adenomas. In this latter group superimposable levels were detected three days before and during transsphenoidal microsurgery. Interestingly, ir-dyn A levels evaluated in extracts of hypothalamic-hypophysial plasma obtained during surgery, just after tumor removal, were 4-5 times higher than in peripheral plasma. Reverse-phase high performance liquid chromatography (rp-HPLC) of extracts of peripheral plasma samples revealed two immunoreactive peaks. The major form had the same retention time of dyn A-(1-32); whereas a second, more lipophilic, peak eluted later and was not further characterized. In contrast, rp-HPLC analysis of extracts of plasma collected from the suprapituitary region displayed only one peak eluting in the position of synthetic dyn A-(1-17). The presence of dyn-related peptides in hypothalamic-hypophysial plasma supports the hypothesis that they may play a part in the regulation of hypothalamic and/or pituitary functions in humans.