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Met-enkephalin and catecholamine release during feline intestinal ischemia-reperfusion
1Department of Anesthesiology and Intensive Care and Surgery, Sahlgrenska University Hospital, Göteborg, Sweden.
Abstract:
Release of met-enkephalin-like immunoreactivity (MLI) into the circulation was investigated during feline intestinal ischemia-reperfusion in relation to the mass of ischemic tissue and in correlation to the sympathoadrenergic, response as gauged by plasma norepinephrine (NE) and epinephrine (E) levels. Chloralose anesthetized cats were randomized to a control group (C, n = 7), 20 cm segmental (S, n = 7), or complete intestinal ischemia (l, n = 7) for 90 min followed by reperfusion for 180 min. MLI and NE/E concentrations were assayed by radioimmunoassay and chromatography, respectively. Severe mucosal lesions and cardiovascular decompensation were observed in l animals in association with increased MLI and NE levels in femoral venous and portal venous plasma, whereas no such responses were observed in the S or C groups. MLI and NE concentrations were consistently higher in portal venous than in femoral venous plasma in 1 animals and correlations between MLI and NE levels were found during reperfusion in the portal, but not the systemic, circulation. Concentrations of E remained unchanged in all groups and did not correlate to MLI release. We conclude that: 1) intestinal MLI release and sympathetic activation occur only when the ischemic insult is sufficient to cause circulatory collapse, characteristic of an "on-off" rather than a "dose-response" pattern; and 2) intestinal MLI and NE release at reperfusion are correlated whereas MLI and E release do not appear to be related events.
Insights
Severe intestinal ischemia triggers met-enkephalin-like immunoreactivity (MLI) and sympathetic nervous system activation. This response, linked to norepinephrine, occurs only during circulatory collapse, not with less severe ischemia.
Area of Science:
- Gastroenterology
- Physiology
- Neuroendocrinology
Background:
- Intestinal ischemia-reperfusion (I/R) injury is a significant clinical concern.
- The role of endogenous opioids like met-enkephalin in I/R is not fully understood.
- Sympathoadrenergic responses during intestinal I/R require further elucidation.
Purpose of the Study:
- To investigate the release of met-enkephalin-like immunoreactivity (MLI) into circulation during feline intestinal I/R.
- To correlate MLI release with the extent of ischemic tissue and sympathoadrenergic response (norepinephrine and epinephrine levels).
- To determine the relationship between MLI, norepinephrine, and epinephrine during intestinal I/R.
Main Methods:
- Feline model of intestinal ischemia (segmental vs. complete) for 90 minutes followed by 180 minutes of reperfusion.
- Measurement of MLI using radioimmunoassay.
- Quantification of plasma norepinephrine (NE) and epinephrine (E) using chromatography.
- Comparison of MLI and catecholamine levels between control, segmental ischemia, and complete ischemia groups.
Main Results:
- Complete intestinal ischemia induced severe mucosal lesions and cardiovascular decompensation.
- Increased MLI and NE levels were observed in portal and femoral venous plasma in the complete ischemia group.
- MLI and NE concentrations were higher in portal than femoral venous plasma, with a correlation during reperfusion in the portal circulation.
- Epinephrine levels remained unchanged and did not correlate with MLI release.
Conclusions:
- Intestinal MLI release and sympathetic activation during I/R occur only with severe ischemia leading to circulatory collapse, suggesting an 'on-off' rather than 'dose-response' pattern.
- MLI and NE release are correlated during intestinal reperfusion, but MLI and E release are not.
- These findings highlight the complex interplay between endogenous opioids and the sympathetic nervous system in severe intestinal injury.