Transient increases in the activities of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAM-DC), key enzymes in polyamine biosynthesis, may be critical to initiation of cell growth. We now report that such increases in ODC (X170) and SAM-DC (X83) activities, and their synthetic products putrescine (X4) and spermidine (X2), occur in rat ileal mucosa between days 1 and 4 after 50% intestinal resection. This is the time period of initiation of mucosal cell hyperplasia in intestinal adaptation after resection and is characterized by increased mucosal cell proliferation, as measured morphologically and biochemically. Intestinal weight increased by 76% and mucosal thickness by 48%. Mucosal DNA content increased by 67% and mucosal DNA synthesis by 104%. Increased intestinal crypt cell proliferation was manifested by a 120% increase in labeling per crypt and a 152% increase in crypt cell production rate (CCPR). The increase in ODC activity was closely associated with the increases in CCPR and rate of villus lengthening. Rates of mucosal cell proliferation, as measured by CCPR, and villus and crypt lengthening were significantly correlated with ODC activity (r = 0.97, 0.98, and 0.94, respectively; P less than 0.01 for all). Our results indicate that the increase in ODC activity, SAM-DC activity, and polyamine biosynthesis is closely associated with the process of adaptive postresectional crypt cell proliferation.
Effects of different phytosterol analogs on colonic mucosal cell proliferation in hamsters
