O . Peulen et al. Livestock Production Science 66 2000 109 –120
111
al., 1995, goat Poszaj et al., 1997 and human which was never observed after weaning. Neverthe-
female Sanguansermsri et al., 1974; Pollack et al., less, irreversibility of normal intestinal maturation
1992; Romain et al., 1992; Buts et al., 1995. In has never been proven, maybe because adult rat diets
general, goat’s colostrum and milk are rich in always contain high polyamine levels as compared
polyamines, and concentrations are higher than those with rat milk Pollack et al., 1992; Romain et al.,
in milk of the other mammals. Polyamine concen- 1992 see later and because intestinal microflora
trations vary with the diet, species, time of lactation, synthesise polyamines Osborne and Seidel, 1990.
total litter weight, offspring number and milking Thus, it may be suggested that dietary polyamines
time. Although there are no data demonstrating a are furnished at such an amount after weaning that
role of dietary polyamines in maturation of the postnatal maturation cannot return to its suckling
digestive tract except maybe in babies, there is also state.
no data disproving this possibility. Therefore, experiments were performed in order to
reduce, where possible, all sources providing poly- amines to the intestine of adult rats Deloyer et al.,
3. Role of dietary spermine in intestinal 1996b. By using germ-free animals, the polyamine
development supply from intestinal microflora was avoided. Diet-
ary polyamines were reduced by giving a specially As spermine could play an important role in the
defined diet to the rats. Endogenous synthesis of intestinal maturation occurring at weaning, it is
polyamines was limited by administration of DFMO useful to carefully analyse its morphological and
and methylglyoxal bis guanylhydrazone MGBG, an biochemical effects, and its mode of action.
inhibitor of S-adenosylmethionine decarboxylase and Peulen et al. 1998b, and unpublished results
of plasma membrane permeability to polyamines. confirmed, in the rat, that during the first 3 days of
This treatment allowed Deloyer et al. 1996b to spermine treatment see earlier, the evolution of the
observe that: 1 rats with intact intestinal microflora following parameters was similar in both natural and
had higher SAs of maltase and higher amounts of in spermine-induced maturation of the intestine:
spermidine and spermine, but lower lactase SA, than proteins, RNA and DNA concentrations of the
pathogen-free animals; 2 a low polyamine diet intestinal mucosa, SAs of brush border disaccharid-
given to germ-free rats had little effect on the ases, such as lactase, maltase and sucrase, morpholo-
functional variables analysed sucrase, maltase and gy of small intestine mucosa and ultrastructure of
lactase SAs and did not modify the intracellular enterocytes, as well as alkaline phosphatase SA,
amounts of polyamines; 3 DFMO and or MGBG TNF-a plasma concentration and gene expression
administered to germ-free rats receiving a low cdx-
1, cdx-2, L-FABP and APO A4 . Consequently, polyamine diet induced modifications in most of the
it was proposed that spermine-induced intestinal variables studied; 4 body weight and wet weight of
maturation is identical to the normal intestinal matu- the proximal and distal intestine decreased, disac-
ration which occurs at weaning. charidase SA decreased and polyamine amounts
However, other observations do not agree with changed according to the inhibitor used.
this conclusion: this phenomenon did not appear As a whole, these results indicate that the supply
irreversible Georges et al., 1990, was not main- of polyamines by microflora or by the diet is not
tained for a long period Deloyer et al., 1996a and a essential for the maintenance of intestinal properties
strong desquamation of the intestinal epithelium see and that a restriction of polyamines, both endogen-
later was not observed at weaning. ous and exogenous, alters general properties of the
Indeed, results indicate that an interruption in the organism as well as intestinal functions. Whatever
spermine treatment for the experimental conditions the treatment applied, modifications of variables
usually chosen 8 mmol day, once a day, for 3 days indicating an ‘‘unmaturation’’ of enterocytes i.e., a
was followed by an involution of the enterocyte decrease in maltase and sucrase SAs, an increase in
differentiation Georges et al., 1990, a phenomenon lactase SA and a modification in the ultrastructural
112 O
. Peulen et al. Livestock Production Science 66 2000 109 –120
aspect of distal enterocytes were never observed. spermine orally is an important observation, giving
Consequently, at weaning or just after this period, researchers an excellent model in order to investigate
irreversible modifications of gene expression could the development of the intestine.
occur in the crypt stem cells, probably as a result of a biological clock effect or of the new hormonal
status of the animals see later.
4. Evolution of different intestinal variables
