Met-enkephalin and catecholamine release during feline intestinal ischemia-reperfusion.

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.