Distribution of polyamines and their biosynthetic enzymes in intestinal adaptation.

Ornithine decarboxylase (ODC) and the polyamines have been shown to be important for growth processes in the intestinal mucosa. The highest activity of ODC is found in the differentiated, nonproliferating villus-tip cells rather than in the rapidly proliferating undifferentiated crypt cells. During poststarvation refeeding and lactation, we now show that increases in ODC activity paralleled the time course of mucosal hyperplasia and thymidine incorporation. Increases in ODC (threefold) were similar in villus and crypt cells, and the villus-crypt gradient of decreasing ODC activity (40:1) was maintained. The activity of the other polyamine biosynthetic enzyme, S-adenosylmethionine decarboxylase (SDC), was highest in the crypt cells in the basal state and increased throughout the entire villus-crypt axis during refeeding and lactation, preserving a villus-crypt gradient opposite to that of ODC. During hyperplasia, all three polyamines increased. Putrescine was highest in the villus-tip cells, paralleling ODC activity, whereas spermidine and spermine were highest in the crypt cells and paralleled the distribution of SDC activity. Thus SDC activity and spermidine and spermine content may play a more important role than ODC and putrescine in regulation of intestinal mucosal proliferation. It is also possible that the threefold increases in the low levels of ODC in the crypt cells are adequate to trigger cell proliferation, whereas the higher ODC levels in villus cells may represent an association with the differentiation of the enterocytes.