AJP - Gastrointestinal and Liver Physiology, Vol 268, Issue 2 260-G269, Copyright © 1995 by American Physiological Society
Hemileaflet susceptibility to oxidative damage in the intestinal brush-border membrane
D. Jourd'heuil, S. Mehta and J. B. Meddings
Gastrointestinal Research Group, Faculty of Medicine, University of Calgary, Alberta, Canada.
Oxidation of biological membranes is characteristic of many types of tissue
injury, including those observed with inflammatory bowel disease. The lipid
compositions of the inner and outer leaflets of biological membranes differ
significantly, making one leaflet theoretically more susceptible to
oxidative stress than the other. In this study, we evaluated the
susceptibility of each membrane hemileaflet for peroxyl radical-mediated
oxidation. In vitro peroxidation of intestinal brush-border membrane was
initiated with the peroxyl radical-generator
2,2'-azobis-(2-amidinopropane)hydrochloric acid (AAPH). Oxidation events
were monitored by following the oxidation-sensitive degradation of the
lipid-soluble fluorescent probe cis-parinaric acid (PnA). The degradation
patterns were clearly distinct in the inner and outer hemileaflet. PnA
degradation in the inner hemileaflet was consistent with a slow first-order
reaction, whereas degradation in the outer leaflet appeared as two
first-order processes delayed in time. The results suggest that the sum of
available antioxidants and endogenous substrates for oxidation are consumed
more rapidly in the outer membrane hemileaflet, making this leaflet more
susceptible to peroxidation compared with the cytofacial leaflet.
