[en] Spermine is a low molecular weight polyamine involved in the postnatal maturation of the gut. When it is administered orally to suckling rats it induces the maturation of their spleen, liver, pancreas, and small intestine. We showed that this polyamine modulates differently the activity of alkaline phosphatase in jejunum and ileum in suckling rat. In 14-day-old rat which had received spermine orally for 3 days, once daily, an increase of alkaline phosphatase activity in the jejunum and a decrease of this activity in the ileum was observed. Alkaline phosphatase was located at the bottom of the villus in the control jejunum and in the whole length of the villus in spermine-treated rats. On the contrary, in ileum of controls, this enzyme was present in the whole length of the villus but disappeared in the spermine-treated animals. An enzyme mass shift was observed in the small intestine after spermine administration. Spermine administration did not change the expression of genes coding for alkaline phosphatase, suggesting a post-transcriptional modification. (C) 2004 Elsevier SAS. All rights reserved.