Related Experiment Videos
Degranulation enhances release of a stable contractile factor from rabbit polymorphonuclear leukocytes
J R Hamilton1, J L Hart, O L Woodman
1Department of Pharmacology, University of Melbourne, Parkville, Victoria, Australia.
The American Journal of Physiology
|June 5, 1998
Summary
Polymorphonuclear leukocytes (PMNs) spontaneously release a protein vasoconstrictor in vitro. PMN degranulation enhances the release rate of this factor, potentially contributing to impaired blood flow during inflammation and reperfusion.
Area of Science:
- Biochemistry
- Physiology
- Immunology
Background:
- Polymorphonuclear leukocytes (PMNs) play a role in inflammatory processes.
- Impaired blood flow during postischemic reperfusion is a clinical concern.
- The contribution of PMN-derived factors to vascular dysfunction requires further investigation.
Purpose of the Study:
- To investigate the release of contractile factors from isolated rabbit PMNs.
- To determine if PMN stimulation or degranulation affects the release of these contractile factors.
- To characterize the nature of the PMN-derived contractile substance.
Main Methods:
- Isolated rabbit PMNs were incubated in Tyrode buffer under various conditions: unstimulated, stimulated with N-formylmethionyl-leucyl-phenylalanine (FMLP), or degranulated with cytochalasin B and FMLP.
- The supernatant from PMN incubations was applied to isolated rabbit aorta to assess contractile activity.
- Contractile activity was also assessed after heat or protease treatment of PMN-derived products.
Main Results:
- Products from unstimulated PMNs incubated for 60 minutes induced greater aortic contraction than those from 5-minute incubations.
- Degranulated PMNs released factors causing significantly greater aortic contraction compared to non-degranulated PMNs.
- The contractile activity was abolished by heat and protease treatment, indicating a protein nature.
Conclusions:
- A stable, proteinaceous vasoconstrictor is spontaneously released by PMNs in vitro at a slow rate.
- PMN degranulation enhances the release rate of this contractile factor.
- These findings suggest that PMN-derived contractile factors may contribute to impaired blood flow in inflammatory conditions like postischemic reperfusion.