To evaluate the role of dietary polyamines in maturation of the rat small intestine, spermine was given orally twice daily to suckling pups from day 10 to day 14 postpartum at different doses: 0, 0.2, 0.5, 1, 2.5, and 5 mumol/dose. Compared to saline treated controls, spermine (5 mumol) produced significant increases in mucosal mass parameters (+12 to +57%, P < 0.05), induced prematurely an adult pattern of microvillous enzymes, and enhanced, respectively, by 19- and 3.5-fold (P < 0.01 vs controls) the concentration of the secretory component of p-immunoglobulins in villous and crypt cells. The response of microvillous enzymes (lactase, sucrase, maltase, and aminopeptidase) to spermine was dose-dependent and -specific since oral administration of arginine (5 mumol) or ornithine (5 mumol) was without effect. Intestinal changes were found to be significant (P < 0.05) for doses of spermine exceeding 1 mumol/day, which is in the range of the amount of polyamines provided by solid pellets at weaning (0.4 mumol/g). However, intestinal changes were undetectable at the physiological amounts of polyamines consumed by pups from rat milk during the suckling period (less than 0.3 mumol/day). Consistent with a direct effect of spermine on the intestinal cell, the cytosolic activity of ornithine decarboxylase was depressed by 27-fold (P < 0.005 vs controls) in the jejunum, while inhibition of ornithine decarboxylase by alpha-difluoromethylornithine did markedly decrease but did not suppress the cell response to spermine. Alternately, plasma corticosteronemia, which was virtually absent by day 14 in controls, ranged between 1.4 and 4.6 micrograms/dl in 60% (N = 9) of the spermine-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

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