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Stress-induced peptide release from rat intermediate pituitary. An ultrastructural analysis
J A Carr1, L C Saland, A Samora
1Department of Anatomy, School of Medicine, University of New Mexico, Albuquerque 87131.
Cell and Tissue Research
|September 1, 1990
Summary
Acute restraint stress increases alpha-melanocyte-stimulating hormone (alpha-MSH) and beta-endorphin release from the rat pituitary intermediate lobe (IL). Ultrastructural analysis confirmed reduced secretory granules in IL cells, indicating peptide release during stress.
Area of Science:
- Neuroendocrinology
- Cell Biology
- Stress Physiology
Background:
- The intermediate lobe (IL) of the pituitary gland is crucial for hormone production and release.
- Alpha-melanocyte-stimulating hormone (alpha-MSH) and beta-endorphin are key peptides synthesized and released by the IL.
- Stress can significantly impact neuroendocrine function, including peptide release from the pituitary.
Purpose of the Study:
- To investigate the ultrastructural evidence of alpha-melanocyte-stimulating hormone (alpha-MSH) and beta-endorphin release from the rat pituitary intermediate lobe (IL) under acute restraint stress.
- To correlate plasma levels of alpha-MSH and beta-endorphin with ultrastructural changes in IL cells.
Main Methods:
- Rats were subjected to acute restraint stress.
- Plasma levels of alpha-MSH and beta-endorphin were measured using radioimmunoassay (RIA) for immunoreactivity (ir).
- Ultrastructural analysis of IL cells was performed using electron microscopy to quantify secretory granules and assess peptide synthesis.
Main Results:
- Plasma alpha-MSH-ir levels increased at 20 and 30 minutes of restraint.
- Plasma beta-endorphin-ir levels peaked at 10 minutes post-restraint.
- Ultrastructural examination showed a significant decrease in the number of secretory granules in IL cells of stressed rats.
- Analysis of immature secretory granules indicated no enhanced peptide synthesis within 30 minutes of restraint.
Conclusions:
- Acute restraint stress leads to enhanced release of alpha-MSH and beta-endorphin from the rat pituitary IL.
- Ultrastructural changes, specifically the reduction in secretory granules, provide direct evidence of peptide release during stress.
- Quantitative ultrastructural analysis is a valid method for assessing peptide release from IL secretory cells in response to physiological challenges like stress.