Acute morphological changes in guinea-pig ileum myenteric neurons after ischemia in situ with superfusion in vitro.

We evaluated changes involving the myenteric neurons of the guinea pig after different times of ischemia in situ followed by superfusion in vitro. Intestinal ischemia was produced by clamping the superior mesenteric artery and maintaining it for 5, 10, 20, 40, 80, or 160 min. Myenteric plexus-longitudinal muscle preparations from ischemic and non-ischemic portions, obtained from the same guinea pig, were dissected and mounted in organ baths containing Krebs bicarbonate solution at 37 degrees C, gassed with 95% O(2) and 5% CO(2). After 2 h of superfusion, ischemic and non-ischemic strips were removed, immersed in a fixative solution, and processed for light and electron microscopy. We found that ultrastructural neuronal changes, which corresponded with light microscopy findings, developed over time. Some structural changes started after 10 min of ischemia, including cell swelling, chromatin clumping, vacuolization, and disruption of protoplasmic and mitochondrial membranes. Smooth muscle cells changes paralleled those observed in the myenteric neurons, but were evidenced until 40 min of ischemia were completed. These results show that ischemia produces acute time-dependent structural changes in the guinea-pig small intestine, and that affected cells exhibit primarily morphological changes characteristic of necrosis.